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CCNA 3.0

Version 1

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CCNA FOUNDATIONS .................................................................................................. 4 OSI Model....................................................................................................................... 4 Upper Layer .................................................................................................................... 5 Lower Layers .................................................................................................................. 5 Data Link Layer Tasks.................................................................................................... 6 Network Layer Tasks...................................................................................................... 7 Transport Layer Tasks .................................................................................................... 8 LAN Physical Layer Implementations............................................................................ 8

CISCO DEVICE BASICS.............................................................................................. 10 Command Modes .......................................................................................................... 10 Basis Switch Commands............................................................................................... 11 Switch Configuration using the Command Line .......................................................... 11 Basic Router Information.............................................................................................. 12 Common CLI Error Messages ...................................................................................... 12 Basic Router Commands............................................................................................... 13 Advance Router Configuration ..................................................................................... 14

OBTAINING NETWORK INFORMATION .............................................................. 16 CDP............................................................................................................................... 16 CDP Related Commands .............................................................................................. 16 Telnet Application ........................................................................................................ 17 Router Basics ................................................................................................................ 18 Router components ....................................................................................................... 18

CATALYST 1900 SWITCH .......................................................................................... 21 Functions....................................................................................................................... 21 Frame Decisions............................................................................................................ 21 Avoiding Loops ............................................................................................................ 21 Spanning Tree Protocol................................................................................................. 22 Spanning Tree Path Cost............................................................................................... 23 Spanning Tree Protocol elections ................................................................................. 23 Spanning Tree States..................................................................................................... 24 How Frame Are Sent .................................................................................................... 24 Switch communication.................................................................................................. 25 Catalyst 1900 Switch Configuration............................................................................. 25 Configuration commands.............................................................................................. 26 Virtual LANs ................................................................................................................ 27

TCP/IP ............................................................................................................................. 28 TCP Connection Establishment .................................................................................... 29 Windowing.................................................................................................................... 29 TCP/IP Internet Layer................................................................................................... 29 ICMP............................................................................................................................. 30 IP Addressing Basics .................................................................................................... 30

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Address Classes ............................................................................................................ 31 Broadcast....................................................................................................................... 32 Subnetting ..................................................................................................................... 33 Configuring IP Addresses ............................................................................................. 35

ROUTING 101 ................................................................................................................ 36 Route Selection ............................................................................................................. 36 Routing Protocols.......................................................................................................... 37 Administrative Distance................................................................................................ 37 Routing Protocol Classes .............................................................................................. 37 RIP ................................................................................................................................ 40 IGRP ............................................................................................................................. 40

ACCESS LISTS .............................................................................................................. 42 Access List Types ......................................................................................................... 42 Access List Guidelines.................................................................................................. 42 Standard IP Access List ................................................................................................ 43 Extended IP Access Lists.............................................................................................. 45 Verifying and Monitoring Access Lists........................................................................ 46

NOVELL INTERNETWORK PACKET EXCHANGE (IPX) PROTOCOL SUITE........................................................................................................................................... 47

IPX ................................................................................................................................ 47 Encapsulation Types ..................................................................................................... 48

CISCO AND WIDE AREA NETWORK (WAN) ........................................................ 50 WAN Connection Types............................................................................................... 50 WAN Layer 2 Encapsulation ........................................................................................ 50 HDLC............................................................................................................................ 51 PPP................................................................................................................................ 51 ISDN ............................................................................................................................. 52

FRAME RELAY............................................................................................................. 54 LMI ............................................................................................................................... 54 Subinterface Connection Types .................................................................................... 55 Obtain Frame Relay Information .................................................................................. 56

LABS ................................................................................................................................ 57

Lab 1 – Configure a name and passwords for a router ................................................. 57 Lab 2 – Configuring Router Interfaces ......................................................................... 59 Lab 3 – Configuring Static Routes................................................................................ 61 Lab 4 – Configuring RIP and Restoring Configuration................................................ 62 Lab 5 – Configuring IGRP............................................................................................ 63 Lab 6 – Access List....................................................................................................... 64

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CCNA Foundations

OSI Model

One of the keys to understanding Cisco is the OSI model. The OSI model permits people to understand how internetwork works and it serves as a guideline or framework for creating and implementing network standards, devices, and internetworking schemes. Some of the advantages of the OSI model include:

• It allows for the breaking down of complex operation into simple elements; • Enables engineers to specialize the design and development of modular elements;

and • It provides standards for plug and play and multivendor integration.

The OSI reference model has 7 layers:

To assist in remembering the OSI model layers in the proper area you might want to try either of the following sentences:

All Application People Presentation Seem Session To Transport Need Network Data Data Link Processing Physical

Appliction (Upper) Layers

Application

Presentation

Session

Transport Layer

Network Layer

Data Link Layer

Presentation Layer

Data Flow Layers

Media Access Control (MAC) Sublayer

Logical Link Control (LLC) Sublayer

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Or from the bottom of the OSI model to the top

Please Do Not Throw Sausage Pizza Away.

Upper Layer

Upper Layers – The upper layers of the OSI model deal with user interface, data formatting, and application access. Specifically these layers do the following:

Application Layer – this is where the user/applications access the network. Presentation layer – determines how data is presented and special processing such as encryption. Session Layer – controls the establishment the establishing, managing and terminating communications sessions between presentation layers.

Lower Layers

The four lower layers are in charge of how data is transferred across a physical wire, through internetwork devices, to desired end station, and finally to the application on the other side. Specifically these layers do the following:

Transport – provides for both reliable and unreliable delivery and error correction before retransmit. Network – provides logical addressing which device us for path destinations Data Link – Combines bits into bytes and bytes into frames, provided access to media using MAC addresses, and error detection. Physical – responsible to move bits between devices and specifies voltage, wire speed and pin-out cables.

Encapsulation

The method of passing data down the stack and adding headers and trailers is called encapsulation. For the each of the lower four layers the unit are as follows:

Transport Segment Network Packet Data Link Frame Physical Bits

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Collision vs Broadcast Domains

Collision domain is a group of devices connected to the same physical media such that if two devices access the media at the same time, the result is a collision of the two signals.

Broadcast Domains is a group of devices in the network that receive one another’s broadcast messages.

Data Link Layer Tasks

The data link layer provides network traffic with information on where it is to go and what it is to do once it gets there. In order to provide this functions the IEEE data link layer is defined into two sublayers:

1. Media Access Control (MAC) Sublayer (802.3) – This sublayers is responsible for how the data is transported over the physical wire. This is the part of the data link layer that communicates downward to the physical layer.

The MAC address is a 48-bit address expressed as 12 hexadecimal digits. The first 24 bits or 6 hexadecimal digits of the MAC address contain a manufacturer identification or vendor code. This can also be called the Organizationally Unique Identifier (OUI). The last 24 bits or 6 hexadecimal are administered by each vendor and often represents the interface serial number.

2. Logical Link Control (LLC) Sublayer (802.2) – This sublayer is responsible for logically identifying different protocol types and then encapsulating them in the order to be transmitted across the network.

The data link layer has two types of devices: bridges and Layer 2 switches. Layer 2 switching is hardware-based bridging. When a bridge hears a frame on the network it must decide to filter, flood or copy the frame onto another segment.

This is decided as follows:

1. If the destination in on the same segment it is filtered. That is, if the frame is

from the same segment then it is blocked from going onto segments. 2. If the destination is on another segment it is forwarded to the proper segment. 3. If the destination is not known to the bridge then the bridge will flood the

frame. That is, it is sent to all other segment other than the originating one.

Bridged/switched networks have the following characteristics:

1. Each segment is a collision domain.

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2. All devices connected to the same bridge/switch are part of the same broadcast domain.

3. All segments must use the same data link layer implementation: Ethernet and all Token Ring.

4. In switched environment, there can be one device per segment, and each device can send frames at the same time, thus allowing the primary pathway to be shared.

Network Layer Tasks

The network layer defines how to transport traffic between devices that are not locally attached in the same broadcast domain. In order for this to occur the following is required:

1. A logical address associated with the source and destination stations. 2. A path through the network to reach the desired destination.

The logical network address consists of two parts: one part to identify the network and the other to uniquely identify the host.

Routers work at the network level. The router performs the following tasks:

• Routers identify networks and provide connectivity. • Router do not forward Layer 2 broadcast or multicast frames. • Routers attempt to determine the optimal path through a routed network based on

routing algorithms. • Routers strip Layer 2 frames and forward packets based on Layer 3 destination

address. • Routers map a single Layer 3 logical address to a single network device;

therefore, routers can limit or secure network traffic based on identifiable attributes within each packet. These options, controlled via access lists, can be applied to inbound or outbound packets.

• Routers can be configured to perform both bridging and routing functions. • Routers provide connectivity between different virtual LANs (VLANs) in a

switched environment. • Routers can be used to deploy quality of service parameters for specified types of

network traffic.

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Transport Layer Tasks For two devices to communicate within a network a connection or session must be established. The transport layer defines the guidelines for the connection between the two devices.

The transport layer define the following functions:

• Allows end stations to assemble and disassemble multiple upper-layer segments

into the same transport layer data stream. This is accomplished by assigning upper-layer application identifiers.

• Allows applications to request reliable data transport between communicating and

systems. This is done through a connection-oriented relationship between the communicating end systems to accomplish the following:

o Ensure the segments delivered will be acknowledged back to the sender. o Provide for retransmission of any segments that are not acknowledged. o Put segments back into their correct sequence order at the receiving

station. o Provide congestion avoidance and control.

LAN Physical Layer Implementations Cabling exist at the Physical Layer of the OSI model. The CCNA exam focus on the Ethernet as the physical and data link connections. The term Ethernet refers to a family of LAN implementations. The three major categories are:

1. Ethernet (DIX) and IEEE 802.3 – this operates at 10 Mbps over coaxial cable,

UTP and fiber. 2. 100 Mbps Ethernet (IEEE 802.3u) – this is also known as the Fast Ethernet that

operates over UTP or fiber. 3. 1000 Mbps Ethernet – this is known as the Gigabit Ethernet that operates at 1000

Mbps over fiber.

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Ethernet Cabling Specifications

Cable Maximum Segment Length

Topology Connector

10Base5 Coax Thick 500 meters Bus AUI 10BaseT Cat 3,4,5 UTP,

2 pair 100 meters Star RJ-45

100BaseTX Cat 5 UTP, 2 pair

100 meters Star RJ-45

100BaseFX Multimode fiber

400 meters Point-to-point Duplex media interface connector (MIC) ST

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Cisco Device Basics

When a switch or a router is first started 3 operations occur: Step 1: The power on self-test (POST) is performed. The device finds hardware and performs hardware checking routines.

Step 2: After the hardware is confirmed functional, the start up routine is performed. The switch/router looks for and loads the operating system software.

Step 3: After the operating system is loaded, the device will find and apply configuration settings that are required for network operations.

Command Modes

Cisco IOS software uses a command-line interface as its traditional console environment. There is two default access levels: user EXEC level and privileged EXEC level. The user EXEC level allows user access to a limited number of basic monitoring commands.

Privileged EXEC level provides access to all router commands. This can be password-protected to allow only authorized users to configure or maintain the router.

When a device is in EXEC mode, this is represented by the > symbol. The following represents this:

hostname>

More commands are accessible from the privilege EXEC mode, to change the device to this mode you would issue the enable command. The switch or router prompt will change to he following:

hostname#

To return to the user EXEC mode you will need to type disable.

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Basis Switch Commands

history – This command will provide you with a list of the contents of the switch’s substitution buffer. You can use the following commands/key strokes to navigate the buffer

Up-arrow button/Ctrl-p – Last (previous) command recall Down-arrow / Ctrl-n – More recent command to buffer Switch>show history – Shows commands buffer contents

show version – this command displays information about software version, system hardware, the names and locations of configuration files, and the boot images. This command enables you to determine the switch’s current operating system which is imperative for troubleshooting.

show interface - this command shows the statistics of all of the switch’s interfaces that are configured. This command can be useful when configuring and troubleshooting the switch.

show ip - this command shows the current IP configuration of the switch.

Switch Configuration using the Command Line

You must switch from the priviledge EXEC mode to the global configuration mode in order change the parameters of the switch.

switch# conf term switch(config)#

To configure an interface you must be in the interface configuration mode. You use the interface command to do this.

switch# interface e0/1 switch(config-if)#

To change the name of the switch you do the following:

switch(config)# hostname testking testking(config)#

Please note the name change is immediate.

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You will also need to configure the ip address of the switch this achieved as follows: testking(config)# ip address 10.5.5.11 255.255.255.0

Basic Router Information

When a router is first turned on it will check its NVRAM (nonvolatile random access memory) for a router configuration. If one is not found then the operating system starts a question driven initial configuration. This is known as the system configuration dialog or setup dialog.

To change the configuration of the router you will need to do so in the configuration mode. There are two levels of modes:

User mode – often used to check the status of the router Privileged mode – used to change the routers configuration. Cisco IOS CLI on Cisco routers offers context sentsitive word help and command syntax help: For word help, use the question mark (?) following one or more characters. This provides a list of commands that begin with a particular character sequence. For command syntax help, use the ? in the place of a keyword or argument. Include a space before the ?.

Common CLI Error Messages

Error % Ambiguous command: “show con”

Reason for error You did not enter enough characters for your switch to recognize the command.

Solution Reenter the command followed by a question mark (?) with no space between the command and the question mark. You will be provided with a choice of keywords that you can enter Error % Imcomplete command.

Reason for error

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You did not enter enough of the keywords or values required. Solution Reenter the command followed by a question mark (?) with no space between the command and the question mark. $ Invalid input detected at ‘^” marker

Reason for error The command was entered incorrectly. The caret (^) marks the place of the error. Solution Enter a question mark (?) to display all the commands that are available in this command mode.

When you are in the command line there are a number of shortcuts or hot keys you can use.

Command Line Editing Key Sequence Description Ctrl-a Moves the cursors to the beginning of the line. Ctrl-e Moves the cursors to the end of the line. Ctrl-f Moves the cursors forward one character. Ctrl-b Moves the cursors backward one character Esc-f Moves the cursors forward one word Esc-b Moves the cursors backward one word Ctrl-d Deletes a single character. Ctrl-k Deletes everything to the right of the cursor. Ctrl-x Deletes everything to the left of the cursor. Ctrl-w Deletes a word. Ctrl-u Deletes a line. Ctrl-r Refreshes the command line and everything typed up to this point. Backspace Removes one character to the left of the cursor. Tab Completes a partially entered command if enough characters have

been entered to make it unambiguous.

Basic Router Commands

show version – this commands displays the configuration of the software version, the router’s hardware, the names and location of the configuration files and the boot images.

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show running-configuration – this commands is used to display the configuration that is being used by the IOS and that is located in the RAM.

show startup-configuration – this commands displays the backup configuration that is located in the NVRAM. This is the file that is used to configure the router during startup.

Advance Router Configuration To make complex and specific configurations for a router you can use the Command Line. To access these specific configuration modes you must first be in the global configuration mode. This is achieved by entering the configure terminal command. Some of the of more popular of these specifc configuration modes are:

Interface – this allows you to enter commands that are responsible to configure operations on each interface. The prompt for this mode is: router(config-if)# Subinterface – this provide support (and configuration) of multiple virtual interfaces on a physical interface. The prompt for this mode is:

router(config-subif)# Line – This mode is used to configure a terminal line. The prompt for this mode is: router(config-line)# Router – This command is used to configure an IP routing protocol. The prompt for this mode is: router(config-router)# To exit one of these specific mode you can use the exit command. This command will return you to the global configuration mode. If you want to totally exit configuration mode you should enter end or Ctrl-z.. These actions will return you to the priviledge EXEC prompt.

copy running-configuration startup-configuration – this command will copy the current configuration in the RAM to the NVRAM (backup configuration).

To change the name of the router you would use the hostname command. An example follows:

router(config)#hostname testking testking(config)#

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To add a Message of the Day you would use the banner motd command. Space and a delimiting character would follow this command. An example follows:

testking(config)#banner motd *

Information Department You must be authorized to use

this system! *

In order to secure your router you can use passwords. Passwords can be used for both the priviledge EXEC mode and on individual lines. All passwords are case sensitive.

To configure a login password for console terminal you would do the following to set the password as england:

testking(config)#line console 0 testking(config-line)#login testking(config-line)#password england

To set a password for an incoming Telnet session you would do the following:

testking(config)#line vty 0 4 testking(onfig-line)#password london

To further secure your router you can provide an enable password. These passwords restricts access to privilege EXEC mode. To encrypt the enable password you would need to use the enable secret command. An example of both commands follows: testking(config)#enable password washington

testking(config)#enable secret boston

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Obtaining Network Information

CDP

The Cisco Discovery Protocol (CDP) discovers and shows information about directly connected devices. CDP is used to manage Cisco devices. This protocol gathers information from directly connected devices (no matter which protocol they are running) and provides administrators with summary of protocol and address information. Devices that support CDP can communicate with each other even if they are running different protocols (TCP/IP and AppleTalk for example) as CDP runs at the data link layer. CDP starts by default when a Cisco device starts.

In general, CDP provides the following information for each CDP neighbor device:

• Device name and if there is one a domain name. • An address for each supported protocol. • Port identifier. That is names of the local and remote ports. This is done is

ASCII such as ethernet0. • Capability lists. • Hardware platform. • Version information.

CDP Related Commands

As stated before CDP is enabled by default on Cisco devices. There will be times that you may want/need to disable it. Two of the reasons for disabling it would be to prevent CDP information from reaching non-CDP devices and to conserve bandwidth. To disable CDP at the device level you would issue the no cdp run command at the global configuration mode. To disable CDP on an interface you would use the no cdp enable command. To re-enable CDP on an interface you would use the cdp enable command.

show cdp neighbours – this command displays the CDP information for each directly connected device. The following information will be displayed for each port:

• Neighbor device ID • Local Interface • The hold time in seconds • Neighbor device capability code • Hardware platform of the neighbor • Neighbor’s remote port ID

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To obtain additional information you can use either the show cdp neighbours detail command or show cdp entry * command.

show cdp entry command will display the following information:

• Neighbor device ID • Layer 3 protocol information • The device’s platform • The device’s capabilities • The local interface type and outgoing remote port ID • The hold time value in seconds • OIS type and version

show cdp traffic – this command displays the number of CDP packets sent and received and the number of errors.

show cdp interface - this command displays the configuration information and the interface status of the local device.

Telnet Application

CDP only provides information about directly connected devices. To obtain information about remote devices you will need to use the Telnet application.

On a router there is no need to use neither telnet nor connect to establish a Telnet session. All you need to do is enter the IP address. For a Catalyst switch you will need to enter the telnet command followed by the IP address of the remote device.

show sessions – this command shows a list of devices that you are connected to. This will allow you to verify Telnet connectivity. This commands displays the following for each device:

• Host name • IP address • Byte count • Amount of time the device has been idle • Connection name assigned to the session

show user – this command displays whether the console port is active, and to list all all active Telnet sessions, with the IP address or IP alias of the originating host. Local connections are represented by con and remote connections are represented vty.

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Ctrl-Shift-6, all together, followed by x will suspend the Telnet connection

resume – this command will resume one session. If there was more than one session before only the last active session will be resumed.

resume sessionnumber (where sessionnumber will be the actual session number) – this command will resume a specific Telnet session. You can use the show sessions command to determine the required session number. To can end a Telnet session you can use the following commands: exit or logout EXEC command while on the remote device to log out of the console session.

disconnect EXEC command while on the local device to end the Telnet session. If you want to disconnect one single session you can use the disconnect sessionnumber (where sessionnumber will be the actual session number) command.

clear line – this command will close a Telnet session from a foreign host. You will need to use the show user command to determine which users are on the device. This will provide you with the lines that need to be disconnected.

Other useful TCP/IP tools that you can use are the ping command and the traceroute command. The ping command verifies connectivity and traceroute will show the route that packets travel.

Router Basics

Booting Sequence of a router

Step 1 – POST Step 2 – Load and run bootstrap code Step 3 – Find the IOS software Step 4 – Load the IOS software Step 5 - Find the configuration Step 6 – Load the configuration Step 7 – Run

Router components

Routers have the following components:

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• RAM – contains the software and data structures that allow the router to function. • ROM – read only memory. Contains microcode for basic functions to start and

maintain the router • Flash memory – the primary use is to contain the IOS software image • NVRAM – this stores the configuration • Configuration Register – this controls how the router boots up. • Interfaces

ROM microcode contains:

• Bootstrap code • POST code • ROM monitor • “Partial” IOS

show version – this command will be display the configuration register value.

copy running-configuration tftp – this will copy the running configuration to a tftp server. This will store a copy of the configuration on a location other than the device.

copy running-configuration startup-configuration – this command will move the running configuration to the startup-configuration (NVRAM). This can be done to save changes to the configuration.

copy startup-configuration running-configuration – this command will move the startup configuration (NVRAM) to the running-configuration (RAM).

As previously stated the Flash memory contains the IOS image. To obtain information about your router memory and image file you can use the show flash command. This command can provide the following:

• Total amount of memory on the router • Memory available • System image file name • The size of the file in Flash

The name of the Cisco image file contains different parts. An example is c2500-js-1_120-3.bin.

c2500 shows the platform that the image runs.

js – j means that this is an enterprise image and s shows an extended capabilities.

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1 – means the file is not compressed and can be moved.

120-3 – represents the version number of the image.

.bin – means that this is a binary executable file.

copy tftp flash – this command will download a new image from a network server to the Flash memory.

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Catalyst 1900 Switch

Functions

This is a Layer 2 device that provides the following functions (bridges provide the same functionality):

• The devices learn the MAC address for all devices attached to each of its ports.

These addresses are stored in a MAC database. • When a frame is received the switch will consult its MAC database to establish

through which port the device can be reached. The frame is only sent to that port. • If your network design includes loops to provide for redundancy it is the switch’s

responsibility to keep the network from coming down but if the Spanning Tree Protocol is configured then backup paths will be allowed.

• An Ethernet switch discovers addresses and functions like a transparent bridge.

The switch keeps a MAC address table used to track the locality of devices connected to the switch. It then employs that table to determine which packet should be forwarded to other segments.

Frame Decisions

When a switch receives a frame that is its MAC table, the frame will only be sent to the port that is associated with that MAC.

When a switch receives a multicast frame or a broadcast frame it is sent to all other ports. This process is referred to as flooding.

Avoiding Loops

Switched and bridge networks are designed with redundant links and devices. This can eliminate single points of failure that would cause a failure of the entire network. This redundant design can cause many problems. The possible problems are:

• Without some form of loop avoidance there is a distinct possibility that each

switch will flood the network with broadcasts continuously. These broadcasts

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can lead a broadcast storm that can cause a waste of bandwidth and severely impacts network and host performance.

• Many copies of nonbroadcast frames may delivered to the destination device.

This could cause unrecoverable errors. • MAC address table could become instable as it receives of the same frame being

received on different ports.

Loop avoidance can address each of these problems.

Broadcast storms are eliminated through a loop avoidance solution would prevent one of the interfaces from transmitting or receiving during normal operations. This can be achieved through using the Spanning Tree. This will be discussed in greater detail.

Database instability results when multiple copies of a frame arrive one different ports of a switch. This can be eliminated through a loop avoidance solution would prevent one of the interfaces from transmitting or receiving during normal operations. This can be achieved through using the Spanning Tree. This will be discussed in greater detail.

A large complex bridged or switched network with multiple switches can cause multiple loops to occur in the switched network. A loop avoidance mechanism is required to eliminate this. This is the main reason for the Spanning Tree Protocol.

Spanning Tree Protocol

DEC developed the Spanning Tree Protocol. It is a bridge-to-bridge protocol. IEEE revised this protocol as the 820.1d specification. The Catalyst 1900 switch uses the IEEE 820.1d specification.

Maintaining a loop-free network is the purpose of the Spanning Tree Protocol. This is achieved as soon as device finds a loop in the network topology it will block one or more of the redundant ports. The Spanning Tree Protocol is ever vigilant and is constantly looking for failures and new additions to the network. When the topology changes, Spanning Tree Protocol will make the required changes to the ports to avoid total loss connectivity or the establishment of new loops.

The Spanning Tree Protocol provides a loop free environment by doing the following:

Electing a root bridge – each broadcast domain will have only one root bridge. All of the ports of the root bridge are called designated ports and are in a forwarding state. A port in a forwarding state can both receive and transmit frames.

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Each nonroot bridge will have on root port – the root port is the one with lowest cost path to the root bridge. These root ports are in the forwarding state. Spanning Tree path cost is an accumulated cost based on bandwidth. If the cost is the same then it is the port with the lowest port number.

On each segment there is one designated port – once again the designated port is selected on the bridge that has the lowest path cost to the root bridge. As these ports are in the forwarding state they are responsible for forwarding the traffic of the segment. Nondesignated ports are in a blocking state so as to break a loop in the topology. As a result it cannot forward traffic.

Devices running the Spanning Tree Protocol exchange Bridge Protocol Data Unit (BPDU). BPDU are multicast message are sent by default is sent every 2 seconds that contain configuration information including the bridge ID. This ID most often contain 2 bytes for priority and 6 bytes that contain the MAC address of the device.

Spanning Tree Path Cost

Link Speed Cost (Reviswed IEEE Specs)

Cost (Old IEEE Specs)

10 Gbps 2 1 1 Gbps 4 1 100 Mbps 19 10 10 Mbps 100 100 The Catalyst Switch 1900 use the old calculations whereas other Catalyst switches , such as 2900XL, use the revised calculations

Spanning Tree Protocol elections

Root bridge – the switch with the lowest bridge ID. Root port – the port(s) with the lowest-cost path to the root. Designated port – all ports on the root bridge are designated ports. On other devices the designated port is the one that has the lowest cost and then the lower bridge ID. Blocking – all ports on the segment that are not designated. Forwarding – all designated ports and root ports are in the forwarding state.

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Spanning Tree States

Spanning tree has the following states: • Blocking • Listening • Learning • Forwarding

These states are moved through by Spanning Tree to maintain a loop free topology. Normally a port is either a blocking state or a forwarding state. When a change is sensed ports temporarily change to the listening and learning states.

All ports start in the blocked state. These port still receive BPDUs. Ports move to the listening state. The move to this state to ensure if the transitions it they will not create a loop. Next the port will populate its MAC address table in the learning state but will not forward frames. Finally the port begin receiving and sending frames once it moves into the forwarding state. The default time to move from the blocking state to the forwarding state is 50 seconds. The time it takes for a device to transition between the listening to learning and learning to forwarding is called forward delay. The default Spanning Tree timers are as follows:

Timer Default Hello Time 2 seconds Forward Delay 30 seconds Max age 20 seconds

How Frame Are Sent

Switches have three operating modes to address frame switching: • Store and Forward – in this mode the switch must first receive all of the frame

prior to forwarding it. The source and destination destinations are read, the CRC (cyclic redundancy check) is done, filters are applied, and then the frame is forwarded. If an error is discovered the frame is dropped. Latency for this mode is dependent on the size of frame.

• Cut-through – this mode only checks the destination address (DA) and then

begins to forward the frame. This can often reduce the latency from input to output port. The delay for this mode is the same no matter the size of the frame. The problem with this mode is that it will forward a frame with an error or a collision frame.

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• Fragment-free – this mode (also referred to as modified cut-through) reads the first 64 bytes of the forwarding frame. In this way collisions can be fiilterd out as they usually occur within the first 64 bytes. The Catalyst 1900 default mode is fragment free switching.

Switch communication

Half-duplex transmission mode implements Ethernet carrier sense multiple access collisions detect (CMSA/CD). This mode is prone to collisions as one line is used for both receiving and sending transmissions. A good parallel is a one lane bridge over a river where cars in one direction must wait for the cars coming the other way are done before moving. Full-duplex Ethernet significantly increase bandwidth are separate circuits (of a twisted pair) are used to transmit and receive frames. This arrangement is collision free. Therefore you effectively double the wires initial bandwidth. Each full duplex connection only uses one port. This is achieved by using point-to-point Ethernet and Fast Ethernet connections.

Catalyst 1900 Switch Configuration

This type of switch can be configured three different ways: • Using the consol port via a menu-driven interface. • Web-based Visual Switch Manager (VSM). • Using the IOS command-line interface (CLI).

As the CCNA exam deals with the use of the CLI so will this study guide.

The default configuration settings of the Catalyst Switch is as follows:

IP address – 0.0.0.0 CDP – Enabled Switching mode – fragment-free 100BaseT port – auto detect duplex mode Spanning Tree – Enabled Console password – none

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Configuration commands

config term – this command will put the switch into the global configuration mode. For example:

switch# conf term switch(config)#

To configure a specific interface (port) you would do the following:

switch(config)# interface e0/1 switch(config-if)#

To configure the IP address and subnet mask on the switch you would do the following:

switch(config)# ip address {address} {mask}

Where address is the IP address and mask is the subnet mask.

To configure the default gateway you would do the following:

switch(config)# ip default-gateway {ip address}

IP address is the IP address of the default gateway such as 10.5.5.3.

To configure the duplex mode of an interface you would do the following:

switch(config)# interface e0/1 switch(config-if)#duplex {auto|full|full-full-control|half}

auto – sets the duplex mode to autonegotiation. This is the default for 100 Mbps TX ports. full – sets the mode to full-duplex. full-flow-control – sets the mode to full-duplex with flow control. half – set the mode to half duplex mode. This is default option for 10 Mbps TX ports.

show version – user EXEC command to display basic information about hardware and the IOS software version. Also included is memory information and uptime.

copy nvram tftp – this command will upload the running configuration to a TFTP server.

copy tftp nvram – downloads the configuration file from the TFTP server.

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Virtual LANs

A VLAN (Virtual Local Area Network) is a switched network that is logically segmented by communities of interest without regard to the physical location of users. Each port on the Switch can belong to a VLAN. Ports in a VLAN share broadcasts. Ports that do not belong to that VLAN do not share these broadcasts thus improving the overall performance of the network. VLANs remove the physical constraints of workgroup communications. Layer 3 routing provides communications between VLANs. In other words users can be in totally different physical locations and still be on the same VLAN. Likewise users in the same physical location can be on different VLANs. VLANs provide the following benefits:

• Reduced administration costs from solving problems associated with moves and

changes - As users physically move they just have to be re-patched and enabled into their existing VLAN

• Workgroup and network security - You can restrict the number of users in a

VLAN and also prevent another user from joining a VLAN without prior approval from the VLAN network management application.

• Controlled Broadcast activity - Broadcasts are only propagated within the VLAN.

This offers segmentation based on logical constraints.

• Leveraging of existing hub investments - Existing hubs can be plugged into a switch port and assigned a VLAN of their own. This segregates all users on the hub to one VLAN.

• Centralized administration control - VLANs can be centrally administrated.

Inter-Switch Links (ISL) is a Cisco proprietary protocol used to interconnect switches and to maintain VLAN information as traffic goes between switches. ISL provides VLAN capabilities while maintaining full wire-speed performance over Fast Ethernet links in full- or half-duplex mode. It operates in a point to point environment. show spantree – this command will display the Spanning Tree Protocol configuration status of the switch.

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TCP/IP

Another important concept for someone preparing for the CCNA exam is the Transmission Control Protocol/Internet Protocol (TCP/IP) stack. In particular Layer 3 and Layer 4. The TCP/IP model compares to the OSI model as follows:

OSI Model TCP/IP Model The TCP/IP application layer enables the following operations:

Email Network Management File Transfer Name Management Remote login

At the transport layer the following two protocols operate:

TCP – connection orientated protocol/ reliable protocol. UDP – User Datagram Protocol is connectionless and unacknowledged protocol.

Application

Presentation

Session

Transport Layer

Network Layer

Data Link Layer

Presentation Layer

Transport Layer

Internet Layer

Data Link Layer

Presentation Layer

Application

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TCP and UDP both use ports to pass information to the application layers. The most common ports used are:

Port Application 21 FTP 23 Telnet TCP 25 SMTP 53 DNS 69 TFTP UDP 161 SNMP 520 RIP

TCP Connection Establishment

For TCP to establish a connection a three-way handshake must occur. That is, the devices involved in the communication must exchange initial sequence numbers (ISN) and a control bit called SYN (synchronize). There are three steps to establishment of communication:

1. Device 1 sends it SYN to Device 2. 2. Device 2 ACK Device 1 SYN and sends it own SYN. 3. Device 1 ACK Device 2 SYN and sets ACK and SYN bit.

Communication is established.

Windowing

TCP controls the flow of data with windowing. The receiving device reports how many octets it is prepare to receive, a window, from the sending device. TCP window size can change during the duration of the connection. Each acknowledgement contains how many bytes the receiving device can receive. If the window size is set to zero it means the buffer of the receiving device is full and cannot receive any more data. The sending device will not send additional data until an acknowledgement has a window bigger than zero.

TCP/IP Internet Layer

The following protocols operate at the Internet Layer of TCP/IP model:

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1. Internet Protocol (IP) – is a connectionless protocol that provides for a best

effort delivery of datagrams. The content of the datagram is not a concern, rather route to a destination is.

2. Internet Control Message Protocol (ICMP) – provides control and messaging

capabilities.

3. Address Resolution Protocol (ARP) – determines the data link layer address (MAC address) of the destination device for known destination IP address.

4. Reverse Address Resolution Protocol (RARP) – determines the source

network address (IP address for example) when source data link layer address (MAC Address) is known. This is used when a device does not know its own IP address when it comes onto a network.

ICMP

ICMP messages are passed in IP datagram and are implemented to send error and control messages. The ICMP messages include:

• Address request • Address Reply • Destination Unreachable • Echo • Echo Reply • Information Request • Information Reply • Parameter Problem • Redirect • Subnet Mask Request • Time Exceeded • Timestamp • Timestamp Reply

IP Addressing Basics

A host or node is a computer or device on a TCP/IP network. Every TCP/IP node is uniquely identified by its IP address. An IP address consists of a network ID and a host ID. If two different hosts belong to the same network, they have the same network ID. The two hosts will have different host ID's and can communicate with each other locally

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without going through a router. If two hosts have different network ID's, they belong to different segments on the network. They must communicate with each other remotely through a router or default gateway.

An IP address consists of 32 binary bits, where each bit is either a 0 or 1. We write the 32 bits into four 8-bit numbers (octets) separated by a periods. For Example: 11000001 . 00001010 . 00011110 . 00000010 (IP address in binary form) To convert the IP address from binary to decimal form, we convert each of the four 8-bit numbers in each octet according to the following table: Decimal Value 128 64 32 16 8 4 2 1 Octet Value x x x x x x x x

So the first octet in the above binary number would be translated as: Decimal Value 128 64 32 16 8 4 2 1 Octet Value 1 1 0 0 0 0 0 1

Everywhere a 1 appears in the table, the decimal value in that column is added to determine the decimal value of the entire octet.

Or 128 + 64 + 1 = 193

Using the same table to translate the other three octets would give us the following result.

00001010 = 8 + 2 = 10 00011110 = 16 + 8 + 4 + 2 = 30 00000010 = 2 So in decimal form, the above IP address is: 193.10.30. 2

Address Classes An IP address consists of two parts, one identifying the network and one identifying the host. The Class of the address determines which part is the network address and which part is the host address.

There are 5 different address classes. The decimal notation of the very first octet can distinguish classes. The following Address Class table illustrates how you can determine to which class and address belongs.

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Class Range of Network Numbers Network Bits Default Subnet Mask A 1.0.0.0 to 126.0.0.0 8 255.0.0.0 B 128.0.0.0 to 191.255.0.0 16 255.255.0.0 C 192.0.0.0 to 223.255.255.0 24 255.255.0.0 D 224.0.0.0 to 239.255.255.255 Multicast E 240.0.0.0 to 247.255.255.255 Research Please note 127 is reserved for local testing. The local loopback is 127.0.0.1.

The two parts of IP address of 172.16.122.204 is as follows: Network number 172.16 (first 16 bits) and Host number is 122.204 (the remaining 16 bits).

If you are required to determine how many hosts are available for given IP address you can use the following formula:

2N – 2 (where N is the number of bits are in the host portion)

For example:

172.128.0.0

As this is a Class B address the first 16 bits are used for the network. As a result 16 bits remain for host.

216 – 2 = 65534 available host address.

Broadcast

Cisco IOS software support three types of broadcasts:

Flooding Directed broadcasts All subnet broadcast

Flooded broadcast are considered local and are represented by 255.255.255.255.

Directed broadcast are sent to a particular network and are allowed to transit by a router. Directed broadcasts have 1 in the host portion of the address. If you want to send a broadcast to the third subnet of the 172.16 network the address would be 172.16.3.255.

To send a broadcast to all the subnets of 172.16 network the address would be 172.16.255.255.

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If you are provided with an IP address and a subnet mask address you can determine the subnet address, the broadcast address, the first usable address and the last usable address. There is usually a question or two on exams that will require this process. 172 16 2 160

3 172.16.2.160 10101100 00010000 00000010 10100000 1 255.255.255.192 11111111 11111111 11111111 11000000 2 172.16.2.128 9 8 10101100 00010000 00000010 10000000 4 172.16.2.191 10101100 00010000 00000010 10111111 5 172.16.2.129 10101100 00010000 00000010 10000001 6 172.16.2.190 10101100 00010000 00000010 10111110 7

Step 1 Write the 32 bit address in binary notation. Step 2 Write the 32 bit subnet mask in binary just below it. Step 3 Draw a vertical line just after the last contiguous subnet mask 1. Step 4 In arrow just below, place all 0s for the remaining free spaces (to the right of the

line). This will be subnet mask. Step 5 In the next row, to right of the line, place all 1s until you reach 32 bit boundary.

This will be the broadcast address. Step 6 On the right side of the line on the next row, places all 0s in the remaining free

spaces until you reach the last free space. Place a 1 in that freed space. This will be your first usable address.

Step 7 On the right side of the line on the next row, places all 1s in the remaining free spaces until you reach the last free space. Place a 0 in that freed space. This will be your first usable address.

Step 8 Copy down all the bits you wrote in Step 1 for the bit fields of the left of the line in all four lines.

Step 9 Convert the bottom four rows to dotted-decimal.

Subnetting

Subnetting is the process used to divide the total available IP addressed (hosts) for your Network into smaller subnetworks (subnets). For example, the Network ID we used in the discussion above (193.10.30.0). This network would consist of 256 possible IP addresses (193.10.30.0 - 193.10.30.255). We know this because in a Class C address, only the last octet is available for host IDs (0000000 - 11111111) or (0-255). Since 0 is used to identify the whole network and 255 is reserved for broadcasts, which leaves us with 254 possible hosts (193.10.30.1 - 193.10.30.254). Suppose we wanted to divide those 254 addresses up into 6 smaller subnets. Using what is referred to as a Subnet Mask can do this. By looking at the above table we can see Class C addresses all have a default subnet mask of 255.255.255.0. Since the last octet of the subnet mask is 0, it means that the Host IDs have not been subdivided into smaller

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subnets. However, if we choose to divide our network into a few smaller segments (subnets), then we would change the default subnet mask by replacing the last octet with one of the valid subnet masks.

If you are asked to determine subnet masks, number of subnets and the number of host you can refer to the charts below. For some situations will be required to memorize these charts so that you can reproduce them.

Class B Subnet Table

Number of Bits Subnet Mask Number of Subnets Number of Hosts 2 255.255.192.0 2 16382 3 255.255.224.0 6 8190 4 255.255.240.0 14 4094 5 255.255.248.0 30 2046 6 255.255.252.0 62 1022 7 255.255.254.0 126 510 8 255.255.255.0 254 254 9 255.255.255.128 510 126 10 255.255.255.192 1022 62 11 255.255.255.224 2046 30 12 255.255.255.240 4094 14 13 255.255.255.248 8190 6 14 255.255.255.252 16382 2

Class C Subnet Table

Number of Bits Subnet Mask Number of Subnets Number of Hosts 2 255.255.255.192 2 62 3 255.255.255.224 6 30 4 255.255.255.240 14 14 5 255.255.255.248 30 6 6 255.255.255.252 62 2

Whenever you are asked to determine subnet masks, number of hosts and number of subnets you can either use the charts provided above or you can use the method illustrated previously in this guide (converting address and subnet mask to binary).

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Configuring IP Addresses

Switches

To configure a 1900 switch with an IP address you would use the ip address command. For example:

Switch(config)#ip address {ip address} {subnet-mask}

{ip address} – would be the dotted decimal number. {subnet-mask} – would be subnet mask related to the IP address.

To establish a default gateway for your switch you would us the ip default command. For example:

switch(config)#ip default-gateway {ip-address}

{ip-address} - would be the IP address of the device which is the default gateway.

Router

To establish a logical address on a router interface you would use the ip address command. For example:

router(config-if)#ip address {ip-address} {subnet-mask}

The {ip-address} {subnet-mask} parameters are the same as they are for a switch.

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Routing 101

Route Selection

A router has two methods that it can forward packets to a non-directly connected device: • Dynamic routes – Once a routing protocol is configured on a router it will

automatically learn routes. Whenever the network topology changes the routing protocol will update the route information.

• Static routes – These are routes that an administrator manually enters into the

router. If a change occurs in the network topology then the administrator will need to manually change the static routes to reflect the new network topology.

To configure a static route you would us the ip route command. The ip route command parameters are:

ip route {network} {mask} {address|interface} [distance] [permanent]

{network} - is the destination ip address {mask} is the related subnet mask {address – is the address of the next hop rotuer interface} – is the name of the interface used to get to the destination network [distance] – you may provide an administrative distance for the route. More information on administrative distance will be provided shortly [permanent] – you may use this argument to specify that the route will remain even if the router is shut down.

If you wanted to establish a static route to 172.16.2.0, subnet mask of 255.255.255.0, and the next hoop router was 172.16.1.2 the command would be as follows:

router(config)#ip route 172.16.2.0 255.255.255.0 172.16.1.2

To assign a default route to the same location you would enter the following command:

router(config)#ip route 0.0.0.0 0.0.0.0 172.16.1.2

A routing protocols are network layer protocols. They gather information from packets to ascertain information and to maintain their information. Routed protocols, on the other hand, are transport mechanisms for traffic through the use of the packets fields and

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formats. Once a routing protocol has determined the route, routed protocols, such as TCP/IP and IPX, are used by the router to route the traffic.

Routing Protocols

Routing protocols have two major types: • Exterior Gateway Protocols (EGP) – These protocols are used to communicate

information between autonomous systems (AS). An example of EGP is BGP (Border Gateway Protocol).

• Interior Gateway Protocols (IGP) – IGP are the routing protocols inside an AS.

Examples of IGP are RIP (Routing Information Protocol) and IGRP (Interior Gateway Routing Protocol).

Note: AS are a collection of networks under a common administrative domain.

Administrative Distance

Administrative Distances are used to determine the trustworthiness of a route of each route source. The route with the lowest administrative distance will be the one used for routing. Administrative distances can be form 0 to 255. The default administrative distance are indicated in the table below:

Source of Route Default Distance Connected Interface 0 Static Route address 1 EIGRP 90 IGRP 100 OSPF 110 RIP 120 External EIGRP 170 Unknown/Unbelievable 255

Routing Protocol Classes It is generally considered that there are three classes of routing protocols. These classes of routing protocol are:

• Distance Vector

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• Link State • Balance Hybrid

Distance Vector Distance vector based routing algorithms pass periodic copies of a routing table from router to router. Routers send their routing table to all of their directly connected neighbors. This allows for the routers to communicate topology changes and it also allows routers to know the topology of the network through second hand information. RIP and IGRP are Distance Vector Routing Protocols. Routing table updates must occur when the network topology has changed. As with the network discovery process, topology change notification must occur router to router. When an update is received from a neighboring router, the update is compared to its own routing table. Routing tables will only be change if a route with a smaller hop count is discovered. Distance vector routing protocols are open to the following problems:

• Routing Loop – this can occur when the network is slow to converge from a

topology change. As a result, inconsistent route information can occur. • Counting to infinity – can cause packets to be sent around the network

continuously when the required route is down. These problems can be avoid with the following techniques:

• Defining a maximum number of hops - Specify a maximum distance vector metric as infinity. 16 with RIP and 256 with IGRP.

• Split Horizon - If you learn a protocol’s route on an interface, do not send

information about that route back out that interface. • Route Poisoning - Information past out on an interface is marked as unreachable

by setting the hop count to 16 for RIP • Hold Down Timers - Routers ignore network update information for some period

of time. The timers can been reset when:

1. The timer expires. 2. Infinity is finally defined as some maximum number. 3. Another update is received indicating that the original route to the network has

been restored.

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Link State

The Link State Routing algorithm maintains a more complex table of topology information. Routers using a link state routing protocol have a complete understanding and view of the entire network. The Link State algorithm uses Link State Packets (LSP) to inform other routers of distant links. All routers exchange LSP to build a total view of the network. OSPF is a Link State Routing Protocol.

When the topology changes, the first routers to find out sends LSP to all other routers on the internetwork. All routers then re-calculate the best path to any affected route. Link State routing protocols are more intensive in terms of power, memory, and bandwidth required.

The differences between distance vector and link state are as follows:

• Distance Vector gets all its information second hand or gossip whereas link state

routing obtains a total topology of the internetwork. • Distance Vector determines the best path by counting hops. Links State uses a

complex bandwidth analysis. • Distance Vector updates topology changes every 30 seconds as default, which

causes a slow convergence time. Link State can be triggered by topology changes resulting in faster convergence times.

• Link state is harder to setup.

Problems with Link State

Link-state (OSPF) needs lots of processing power to rebuild the routing database (tree). Network bandwidth, is another problem. Link-state info can flood the network. Balanced hybrid approach combines the aspect of the link state and distance vector algorithms. EIGRP is an example of this approach.

To configure dynamic routing protocols you use the following commands:

router(config)#router {protocol}[keyword]

{protocol} – RIP, IGRP, OSPF, or EIGRP [keyword] – stands for a autonomous system. IGRP requires this parameter.

Router(config-router)#network {network number}

{network number} – specifies the directly connected network.

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RIP

If you want to enable RIP on a router that is directly connected to the following networks, 192.168.2.0 and 10.0.0.0 you would use the following commands:

router(config)#router rip router(config-router)#network 192.168.2.0 router(config-router)#network 10.0.0.0

Display RIP associated information

The show ip protocols command displays values associated with routing timers and network information associated with the entire routers.

The show ip route command displays the contents of the IP routing table.

The debug ip rip command displays RIP routing updates as they are sent and received.

IGRP

IGRP is an advance distance vector routing protocol. It offers a number of features that other distance vector protocols do not have. These features are:

• Increased scalability. IGRP default hop count is 100 and its maximum hot count

is 255 hops. • Sophisticated metric. It uses a composite metric. More will follow on this point. • Multiple path support. IGRP can maintain up to six unequal cost paths betweens

a source and destination.

As stated before IGRP uses a composite routing metric. This metric includes the following parts:

• Bandwidth – the lowest bandwidth value in the path. • Delay – the cumulative interface delay on the path. • Reliability – the reliability between source and destination, determine by the

exchange of keepalives. • Load – the load on a link between the source and destination based on bits per

second.

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• MTU – the Maximum Transfer Unit value of the path.

By default only bandwidth and delay are used by the IGRP metric.

To configure IGRP you would use the following combination of commands:

router(config)#router igrp {autonomous-system} router(config-router)#network {network-number}

To enable IGRP on a router, on autonomous system 100, that connects to network 192.168.1.0 and 10.0.0.0 the commands would be:

router#config t router(config)#router igrp 100 router(config-router)#network 192.168.1.0 router(config-router)#network 10.0.0.0

To change the default load balance of IGRP, which is 1 (equal sharing), you use the variance command to configure un-equal cost load balancing by defining the difference between the best metric and worst acceptable metric.

In addition you can use the traffic share command to control how traffic is distributed among IGRP load sharing routes.

Display IGRP related information

The show ip protocol command displays parameters, filters, and network information about the entire router. In addition, it will also provide the autonomous system, routing timers, networks, and administrative distances.

The show ip route command displays the contents of the IP routing table. The table contains a list of all known networks and subnets associated with each entry.

The debug ip igrp events command will display a summary of the IGRP routing information.

By default a router assumes all directly connected subnets are listed in its routing table. If the router receives a packet for an unknown destination address, the packet will be dropped. This can be changed with the ip classess command. With the ip classess command configured if a packet is received for an unknown destination then the packet will be sent to the default route and not dropped.

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Access Lists

Access list can be used to control network traffic. Specifically Access Control Lists (ACLs) are used in routers to classify traffic. Once the traffic is recognized it can then utilized to filter traffic to control the traffic in a network. These filters can be used to either filter the flow in or out of a router interface. Access lists are most often used to filter packets.

Access List Types

There are two types of access lists: • Standard Access Lists – Standard IP access lists check the source address of the

packets that could be routed. It will either permit or deny the packet for the entire protocol suite based on the IP address of the source device.

• Extended Access Lists – Extended IP access lists check for both the source and

destination packet addresses. In addition, they also check for particular protocols, port numbers and further factors that provide administrators more flexibility in specifying the packets to be checked.

Access lists can have the following applications: Inbound access lists – packets are checked before they are process onto an outbound interface. This is the most efficient form of access list, as a packet that is dropped will not be looked up in the routing table. If the packet is accepted it will then be processed for transmission.

Outbound access lists – The packet is sent to the outbound interface from the inbound interface then the accessed list is applied before the packet is routed.

Access List Guidelines

When using access lists you will need to remember the following principles when configuring them:

• Only use the Cisco defined access list numbers based on the protocol and type of

list you are creating.

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• You can only have one access list per protocol for each direction on each interface. An interface can have more than one access list as long as there is only on per protocol.

• Access list are implemented from the top down. Specific references should

appear before general one as more frequent conditions should appear before the less frequent ones. There is an implicit deny at the end of every access list.

• If an access list does not have a permit statement there is an implicit deny all.

• Create the access list before it is applied to the interface. If an access list is

applied before it is created then all traffic is permitted. • Access list only applies to traffic being processed through the router. Traffic from

the router is not filtered.

Protocol Number Range IP Access List Standard 1 to 99 Extended 100 to 199 Named Name (Cisco IOS 11.2 and later) IPX Access List Standard 800 to 899 Extended 900 to 999 Named Name (Cisco IOS 11.2 and later)

Standard IP Access List A standard IP access list analyses the source address of the packet and matches it against the access list. To create an access list in global configuration mode use the following command:

router(config)#access-list {number 1-99} {permit|deny} {source-address} {wildcard- mask}

{number 1-99} – number for the access list. {permit|deny} – whether to permit or deny traffic from the IP address {source-address} – IP address for the source of the packet {wildcard-mask} – which parts of the IP address that must be read and which parts that can be ignored.

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Wildcard Mask

A wildcard mask is 32 bit, 4 octet, address that can be used on a router to allow you to apply an access list to a specific IP address or a specific range of IP addresses. Wildcard masking for IP address bits uses the numbers 1 and 0 to indicate how to treat the corresponding IP address bits:

O in the wildcard mask indicates that the corresponding bit in the IP address must checked.

1 in the wildcard mask indicates that the corresponding bit in the IP address must be ignored.

In the chart below please find some example of wildcard masks and what the mean.

128 64 32 16 8 4 2 1 Meaning 0 0 0 0 0 0 0 0 Check all address bits (match all) 0 0 1 1 1 1 1 1 Ignore the last 6 address bits 0 0 0 0 1 1 1 1 Ignore the last 4 address bits 1 1 1 1 1 0 0 0 0 Check last 2 address bits 1 1 1 1 1 1 1 1 1 Do not check address (ignore bits in octet)

To apply the access list you will need to first identify the interface and then apply it to the interface. The following commands are used:

router(config)#interface serial 0 router(config-if)#ip access-group {access-list-number}{in|out} {access-list-number} – this would be the number of the access list that you want to apply. {in|out} – you can specify if the access list is in or out. By default it is out if it is not specified.

The previous commands are the ones used to apply an access list to a physical interface, if you want to apply an access to a virtual interface the commands are slightly different. A virtual interface is called virtual terminal lines (vty). By default, there are five such virtual terminal lines, numbered vty 0 to vty 4. These are used to Telnet to the command line interface (CLI) of a router. In the case for virtual terminal lines the commands are: router(config)# access-list {number 1-99} {permit|deny} {source-address} {wildcard- mask} router(config)#line vty 0 4 router(config-line)#access-class {access-list-number}{in|out}

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{access-list-number} – this would be the number of the access list that you want to apply. in – prevents a router from receiving Telnet sessions from the IP address in the access list. out – prevents the router vty ports from initiating Telnet connections to addresses defined in the access list.

Extended IP Access Lists

Configuring an extended IP access list is very similar to a standard IP access list. The command to create the list is:

router(config)#cccess-list {number 100-199} {permit|deny} {protocol} {source-address} {source-wildcard} {destination-address} {destination-wildcard} {port} [established] [log]

{protocol} – identify the protocol to be filtered. It can be IP, TCP. UDP, ICMP, GRE or IGRP. {source-address} {source-wildcard} – identify the IP address of the source and its wildcard mask. {destination-address} {destination -wildcard} – identify the IP address of the destination and its wildcard mask. {port} – protocol port number. [established] – is used for inbound TCP only. [log] – sends a logging message to the console. When configuring Extended Access List you should be familiar with the common port numbers:

IP Protocol Well-Known

Port Numbers FTP data 20 FTP program 21 Telnet 23 SMTP 25 TFTP 69 DNS 53

Then you would apply the access list with the following command:

router(config-if)#ip access-group {access-list-number}{in|out}

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Verifying and Monitoring Access Lists

The show ip interface command displays IP interface information and indicates whether any access lists are set for a specific interface. The syntax for this command is as follows:

router#show ip interface {interface-type} {interface-number}

The show access-lists command displays the contents of all access lists. The syntax is as following:

router#show {protocol} access-lists {access-list-number|name}

By entering access list number or name you can view a specific access list. To display the access list for a specific protocol you would identify the protocol.

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Novell Internetwork Packet Exchange (IPX) Protocol Suite

Cisco routers can a sloe be used within a Novell network. Novell has its own proprietary protocol suite. This suite is called Novell IPX/SPX (Internet Packet Exchange/Sequenced Packet Exchange).

IPX

IPX is a: • Does not require an acknowledgment for each packet as it is Connectionless

datagram protocol. It is much like IP and UDP. • Layer 3 protocol that defines the network layer address. This includes a

network.node designator.

Novell Netware has its own proprietary: • IPX RIP to make possible exchange of routing information.

• Service Information Protocol (SAP) to advertise and find network services. An

example is GNS (Get Nearest Server). • Netware Core Protocol (NCP) to provide client to server connections and

application level services. • Sequenced Packet Exchange (SPX) is a Layer 4 connection orientated protocol.

IPX and SPX are very similar to IP and TCP.

Novell IPX addressing uses a two-part address – the network number (32 bits) and the node number (48 bits). The node number is most often the MAC address of network interface.

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Encapsulation Types

IPX has its own encapsulation types but they do Cisco equivalents. These equivalents are listed in the table below.

Media Type IPX Encapsulation Cisco Encapsulation Ethernet Ethernet_802.3 novell-ether (default) Ethernet_802.2 sap Ethernet_II ARPA Ethernet_SNAP snap Token Ring Token-Ring_SNAP snap (default) Token-Ring sap FDDI FDDI_SNAP snap (default FDDI_802.2 sap FDDI_Raw novell-fddie

The ipx routing command enables IPX routing and SAP services. An optional node address can be specified for the serial interface. If no node address is specified, the Cisco router uses the MAC address of the LAN interface. The proper syntax is:

router(config)#ipx routing [node]

The ipx maximum-paths command enables load sharing. The default is 1, meaning no load sharing is enabled. The syntax is:

router(config)#ipx maximum-paths {paths}

{paths} – represents the maximum number of parallel paths to the destination. Default is 1 (no sharing) and the maximum is 512.

To enable IPX routing on an interface you would us the ipx network command. That is:

router(config)#ipx network {network} [encapsulation encapsulation-type]

{network} – this would be the network number. [encapsulation encapsulation-type] – this would help specify an encapsulation type (arpa, novell-ether, novell-fddi, sap and snap).

Standard IPX Access Lists

Standard IPX access lists permit or deny packets based upon the source and destination IPX addresses. This differs from IP where it only looks at the source address. There are

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no wildcard masks with IPX and you can use either the Node Address or Network Address. To configure it you would use the following command:

router(config)# access-list 810 permit 4b 5c

The same, other than wildcard mask, commands are used to create and enable IPX Standard Access Lists and Extended Access Lists as are used for IP.

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Cisco and Wide Area Network (WAN)

WANs make data connections across a broad geographic area. Companies use WAN to connect various company sites to facilitate communication between distance offices. As a result you must use line from a service provider.

WAN Connection Types

There are three general connections types that can be selected from:

Leased line – a leased line, as called point-to-point or dedicated connection, provides a single connection from the customer location through the service provider to the remote company location. This line is not shared (and has a guarantee bandwidth) but they can be very expensive.

Circuit switched – A dedicated link is provided between the sender and receiver location for the duration of the communication. This are often used for WAN usage is only occasional.

Packet switched – Packet switched is a WAN switching method that network devices share a single point-to-point link to transport data (broken down into packets) from source to destination across carrier network. To provide end-to-end connectivity is done by virtual circuits (VC). Packet switching offers service like leased line, except with a shared line, which lowers the cost.

WAN Layer 2 Encapsulation

WAN has a number of encapsulation types that can be used. This include: • Cisco High-Level Data Link Control (HDLC) – the default encapsulation type for

point-to-point dedicated links and circuit-switched connections. • Point-to-Point Protocol (PPP) – this provides router-router and host-to-network

connections over synchronous and asynchronous circuits. It works with both IP and IPX. It has built in security features such as Password Authentication Protocol (PAP) and Challenge Handshake Authentication Protocol (CHAP).

• Serial Line Internet Protocol (SLIP) – is the standard point-to-point serial

connections for TCP/IP. PPP has generally replace SLIP.

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• X.25/Link Access Procedure, Balance (LAPB) – a standard that controls connections between DTE and DCE.

• Frame Relay – is the industry standard for switched data link protocol that

handles virtual circuits. This is the next generation of X.25. • Asynchronous Transfer Mode (ATM) – the international standard for cell relay in

which multiple services types are conveyed in fixed-length cells.

HDLC

As stated earlier Cisco has its own version of HDLC. Cisco HDLC frame includes a proprietary type field that is used to indicate protocol. This makes possible multiple network layer protocols to share the same serial link. To enable this use the following command:

router(config-if)#encapsulation hdlc

PPP

PPP is a data link layer protocol with network services. As a result PPP can be broken into sublayers: data link layer and physical layer. PPP use Network Control Program (NCP) to encapsulate multiple protocols.

PPP session consists of the three stages:

1. Link Establishment 2. Authentication Phase (optional) 3. Network layer protocol phase

To enable PPP authentication you will use the following commands:

router(config)#hostname {name} The router must have name. {name} will be the name you select for the router. If you wanted to call your router testking you would use the following command: router(config)#hostname testking

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Next you need to provide the router with the name and password that should be expected from the remote router. You would use the following command:

testking(config)#username {name} password {password}

Both parameters are case sensitive.

The final step is to configure PPP authentication. The command would be as follows:

testking(config-if)#ppp authentication {chap|chap pap|pap chap|pap}

ISDN

Integrated Services Digital Network (ISDN) is a digital service designed to run over existing telephone networks. ISDN can support both data and voice simultaneously. ISDN encompasses the OSI Physical, Data Link, and Network Layers. ISDN networking can provide up to 128 Kbps with a PPP Multilink connection to corporate networks or the Internet. A Basic Rate Interface (BRI) connection can also be used as a backup line in case the primary link goes down. In this case you have to set the desirability of the ISDN link to be very low. In other words only use if there is no other way.

ISDN has the following benefits over standard telephone connections:

• Data transfer is faster than typical modems • Call setup is faster • ISDN can carry voice, video, and data traffic

ISDN Protocols These protocols deal with ISDN issues:

• E – Specifies ISDN on the existing telephone network. • I – Specifies Concepts, terminology, and Services. • Q – Specifies switching and signaling.

ISDN Function Groups

Devices connected to the ISDN network are known as terminals and have the following types:

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• TE1 – Terminal Equipment type 1 understands ISDN standards. Such as a BRI Interface on a router.

• TE2 – Terminal Equipment type 2 predates ISDN standards. To use a TE2, you must have a Terminal Adapter (TA).

ISDN Reference Points

ISDN uses four different reference points to define logical interfaces. They are as follows:

• R – Defines the reference point between non ISDN equipment and a TA • S – Defines the reference point between user terminals and an NT2 • T – Defines the reference point between NT1 and NT2 devices • U – Defines the reference point between NT1 devices and Line Termination

Equipment. (North America Only)

ISDN offers the following benefits:

• Full-time connectivity is spoofed on routers using DDR • SOHO sites can be cheaply supported • Can be used as a backup for leased lines • Using modem cards can eliminate modem racking

ISDN can either be Basic Rate ISDN (BRI) or Primary Rate ISDN (PRI). BRI is 2 64 Kbps B Channels for data and one 16 Kbps D Channel for link management and connects to NT1 for 4-wire connection. PRI is 23 B Channels and 1 D Channel in the US or 30 B Channel and 1 D Channel in Europe. Occasionally when configuring ISDN you will need to configure a Service Profile ID (SPID). A SPID is a series of characters which can look like phone numbers. These numbers will identify your connection to the Switch at the CO. The SPIDs are processed during each call setup operation.

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Frame Relay

Frame relay is a fast WAN protocol that operates at the Physical and Data Link layers (mostly Data Link layer) of the OSI model. Frame relay is used between DTE and DCE devices. Uses Packet Switching. DTE consists of terminals, PC’s, routers and bridges, all of which are customer owned end node devices. The service provider owns DCE devices such as packet switchers. Frame Relay uses Permanent Virtual Circuits (PVCs). Data Link Connection Identifier (DLCI) is used to identify connection.

Frame Relay offers speeds between 56 Kbps and 2,078 Mbps. However, the default setting for a serial DCE interface is T1. Frame Relay uses a CRC, bad packets are discarded and the receiving station requests re-transmission of any missing frames.

Data Link Connection Identifiers (DLCI) – Used to identify the virtual circuits. DLCIs can be set to a number between 16 and 1007.

LMI

Local Management Interfaces (LMI) – Provide information about the DLCI values and the status of virtual circuits. The default is Cisco but there are 3 possible settings:

• Cisco (Default) • ANSI • Q933a

To set up frame relay on an interface just set the encapsulation to frame-relay. Frame relay encapsulation can either be Cisco (Default) or IETF. You must use Cisco encapsulation to connect two Cisco routers or IETF if a third party router is involved. Frame Relay configuration is done in the interface configuration mode. Although LMI type is configurable, the Cisco router will try to autosense which LMI type the switch is using:

router(config-if)#encapsulation frame-relay {cisco|ietf}

To assign a DLCI to an interface you would type:

router(config-if)#frame-relay interface-dlci {number 16-1007}

To set the LMI type you enter:

router(config-if)#frame-relay lmi-type {cisco|ansi|q933a}

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A keepalive interval must be set to enable LMI on an interface. This is 10 seconds by default and can be set by typing:

router(config-if)#frame-relay keepalive {number of seconds}

Frame Relay Maps The Frame Relay Map tells the network protocol how to get from a specific protocol and address pair to the correct DLCI. There are two ways to make this happen, you can use the frame-relay map command or you can use the inverse-arp function. The “frame-relay map” command can be used to show which routers are reachable.

router(config-if)#frame-relay inverse-arp {protocol} {dlci} router(config-if)#frame-relay map {protocol} {protocol address} {dlci} [broadcast] [cisco|ietf]

With frame-relay you can use subinterfaces to allow multiple virtual circuits on a single serial interface and each subinterface can be treated as a separate interface. You use the interface s0.interface number command:

router(config-if)#interface s0.{subinterface-number} {point-to-point|multipoint}

Subinterface Connection Types

You can configure subinterfaces to support the following connection types: • Point-to-point – A single subinterface is used to establish one PVC connection to

another physical interface on a remote router. Each interface would be on the same subnet and have a single DLCI. Each point-to-point connection is its own subnet and act like a leased line.

• Multipoint – A single subinterface is used to establish multiple PVC connections

to multiple physical interfaces on a remote router. All participating interfaces are in the same subnet and each interface would have it’s own DLCI. The subinterface acts like a NBMA network and broadcasts are subject to split horizon rules. It is worthwhile creating a subinterface with a number that matches the DLCI identifier.

Committed Information Rate (CIR) – the rate, in bits per second, at which the Frame Relay switch agrees to transfer data.

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Obtain Frame Relay Information

To display Frame Relay information you could use the following:

show frame-relay ip - Shows frame relay ip statistics show frame-relay lmi - Shows LMI statistics show frame-relay map - Shows map table show frame-relay pvc - Shows PVC Statistics Also DLCI Info show frame-relay route - Shows frame relay routes show frame-relay traffic - Shows protocol statistics

The show Interface command also shows Frame Relay information on a specific interface. The show ip route command will also show which routers are reachable.

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Labs

Lab 1 – Configure a name and passwords for a router You have been tasked to change some of the configurations on one of your company’s router. Specifically you tasks are:

1. Change the name of the router to test_king. 2. Restrict access to privileged EXEC mode. The password should be Paris.

Task 1 You will need to log onto your router. You should see a prompt that looks like: Router> In order to configure parameters you will need to be the privileged EXEC mode. Therefore the first step will be to use the enable command. Router>enable Router# It is now necessary to enter the global configuration mode. To do this you will need to do the following: Router#config terminal Now you are ready to change the name of your router. You will need to do the following: Router(config)#hostname test_king test_king(config)# Task 2 You now need to configure a password for the router. You will need to do the following: test_king(config)#enable password Paris test_king(config)# You know you need to backup these configuration changes to the startup configuration. You will need to do the following:

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test_king(config)#copy running-configuration startup-configuration test_king(config)# You have completed the tasks assigned to you. It is now time to exit the global configuration mode and the privilege EXEC mode. You will need to do the following: test_king(config)#exit test_king#disable test_king>exit You report back to your supervisor and he says that he forgot to tell you that he also wanted an enable secret password (Denmark) and he wanted a copy of the most current running configuration on the TFTP server (10.1.1.1). You will need to log onto your router. You will need to begin with the enable secret password. You return and take the following actions to start: test_king> test_king>enable Password:***** test_king#config t test_king(config)# Now it is time to configure the new secret password. You will need to do the following: test_king(config)#enable secret Denmark test_king(config)# Now you need to save this change to the startup configuration and then copy the running configuration to TFTP server. You will need to do the following: test_king(config)#copy running startup test_king(config)#copy running-config tftp Address or name of remote host []? 10.1.1.1 Destination filename [running-config]? test_king.fg test_king(config)# Now it is time to exit the router. You will need to do the following: test_king(config)#exit test_king#disable test_king>exit

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Lab 2 – Configuring Router Interfaces Day 1 of your new job has come and gone. You are feeling pretty good about how things have been going. You know a new day brings new challenges and you know you are up for it. You boss says he would like you to work on the router test_king again. You wants you to configure the interfaces on it. On the Ethernet interface 0 he would like the IP address 192.5.5.1 and for the serial interface 0 he needs the IP address 201.100.11.1. He reminds you that this is a 56K connection. You set out to complete your two tasks. You start with the Ethernet interface. You take the following action: test_king>enable Password:******* test_king#config terminal test_king(config)#interface ethernet 0 test_king(config-if)#ip address 192.5.5.1 255.255.255.0 The interface no has an IP address configured. It is now required to enable the interface. You would need to take the following action: test_king(config-if)#no shutdown test_king(config-if)#exit test_king(config)# The Ethernet Interface is now configured and enabled. Time to configure the serial interface. You would need to take the following action: test_king(config)#interface serial 0 test_king(config-if)#ip address 201.100.11.1 255.255.255.0 test_king(config-if)#bandwidth 56 test_king(config-if)#no shutdown test_king(config-if)#exit test_king(config)# You remember that now that you have changed the running configuration you will need to back it up to the NVRAM (startup configuration) and to the TFTPP server. You would need to take the following action: test_king(config)#copy running startup test_king(config)#copy running-config tftp Address or name of remote host []? 10.1.1.1 Destination filename [running-config]? test_king.fg

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test_king(config)#exit test_king#disable test_king>exit

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Lab 3 – Configuring Static Routes Now it is time to configure some static routes for another one of your companies routers (test_king2). The two destinations are 204.204.7.2 and 204.204.7.1. To reach these destinations the traffic will need to traverse 210.100.13.1 and 210.100.13.3 respectively. The enable secret password for test_king2 is Sweden1a. You set off to complete the necessary work. test_king2>enable Password:******** test_king2#config t test_king2(config)#ip route 204.204.7.2 255.255.255.0 210.100.13.1 test_king2(config)#ip route 204.204.7.1 255.255.255.0 210.100.13.3 As is standard for your company you now backup the new configuration. test_king2(config)#copy running startup test_king2(config)#copy running-config tftp Address or name of remote host []? 10.1.1.1 Destination filename [running-config]? test_king2.fg test_king(config)#exit test_king#disable test_king>exit Your boss has changed his mind he want both static routes removed from this test_king2 and the backups to reflect this action. You take the following actions: test_king2>enable Password:******** test_king2#config t test_king2(config)#no ip route 204.204.7.2 255.255.255.0 210.100.13.1 test_king2(config)#no ip route 204.204.7.1 255.255.255.0 210.100.13.3 test_king2(config)#copy running startup test_king2(config)#copy running-config tftp Address or name of remote host []? 10.1.1.1 Destination filename [running-config]? test_king2.fg test_king(config)#exit test_king#disable test_king>exit

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Lab 4 – Configuring RIP and Restoring Configuration Your boss has decided to configure RIP on test_king. He turns to you to complete this task for him. He reminds you to remove the static routes that have been configured. You have just completed removing the static routes off of test_king2 so you are confident that you can complete this task quickly. test_king>enable Password:******* test_king#config terminal test_king(config)#no ip route 172.16.30.0 255.255.255.0 test_king(config)#no ip route 172.16.40.0 255.255.255.0 test_king(config)#no ip route 172.16.50.0 255.255.255.0 test_king(config)#router rip test_king(config-router)#network 192.5.0.0 test_king(config-router)#exit You decided that a change like this should definitely backup this new configuration. You need to take the following actions: test_king(config)#copy running startup test_king(config)#copy running-config tftp Address or name of remote host []? 10.1.1.1 Destination filename [running-config]? test_king.fg test_king(config)#exit test_king#disable test_king>exit A month later your boss says that something has gone wrong with test_king and it needs to be restored. You first thought is “no problem, I’ll just copy startup configuration to the running configuration. Your boss must be reading your mind and tells you that the startup configuration is corrupted. You know that you will need to copy the file from the TFTP server. You need to take the following actions: test_king>enable Password:******* test_king# test_king#copy tftp running-config Address or name of remote host []? 10.1.1.1 Destination filename [running-config]? test_king.fg Accessing tftp://10.1.1.1 (via Ethernet): !! [OK – 487/4096 bytes] 487 bytes copied in 5.400 secs (97 bytes/sec) test_king#

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Lab 5 – Configuring IGRP A test network has been established to test possible future configurations. You decide to use experiment with IGRP. You select tk_a1 to be configured. tk_a1 will be advertising both 210.204.0.0 and 172.16.0.0. tk_a1 has no passwords configured, it’s a test network after all, and belongs to autonomous system 13. You need to take the following actions: tk_a1>enable tk_a1#config terminal tk_a1(config)#router igrp 13 tk_a1(config-router)#network 210.204.0.0 tk_a1(config-router)#network 172.16.0.0 tk_a1(config-router)#exit tk_a1(config)#exit tk_a1#copy running-configuration startup-configuration

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Lab 6 – Access List You have been tasked to prevent ICMP traffic from 204.204.7.2 from reaching test_king. All other IP traffic is to be permitted. To met these objectives you take the following actions: test_king>enable Password: ******* test_king#config t test_king(config)#access-list 103 deny icmp 204.204.7.2 0.0.0.0 any test_king(config)#access list 103 permit ip any any test_king(config)#interface Ethernet 0/0 test_king(config)#ip access-group 101 out test_king(config)#exit You decide to confirm this access list. You take the following actions and receive the following results: test_king#show access-list 103 Extended IP access list 101 deny icmp host 204.204.7.2 any permit ip any any Your boss calls and tells you that he just wanted to give you some practice with access list and now wants you to remove the access list. As a result, you take the following actions: test_king#config t test_king(config)#no access-list 101 test_king(config)#exit test_king#exit test_king> The end result is no change to the running configuration. Therefore there is no need to back it up.