Chapter 1 Introduction to Routing and Packet Forwarding CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College [email protected] Last

Chapter 1Introduction to Routing and Packet Forwarding

CIS 82 Routing Protocols and Concepts

Rick Graziani

Cabrillo College

[email protected]

Last Updated: 2/16/2009

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This Presentation

For detailed information see the notes section within this PowerPoint.

This presentation is based on the Exploration course/book, Routing Protocols and Concepts.

For a copy of this presentation and access to my web site for other CCNA, CCNP, and Wireless resources please email me for a username and password. Email: [email protected] Web Site: www.cabrillo.edu/~rgraziani

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Note This chapter contains mostly introductory material. Most of not all of this information will be explained in more detail

in later chapters or later courses. The bootup process and the IOS are examined in a later

course. Do not worry or focus too much on the details for now. This will all be examined and explained in the following chapters.

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For further information This presentation is an

overview of what is covered in the curriculum/book.

For further explanation and details, please read the chapter/curriculum.

Book: Routing Protocols

and Concepts By Rick Graziani and

Allan Johnson ISBN: 1-58713-206-0 ISBN-13: 978-58713-

206-3

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Topics

Inside the Router Routers are computers Router CPU and Memory Internetwork Operating

System Router Bootup Process Router Ports and Interfaces Routers and the Network

Layer Path Determination and

Switching Function Packet Fields and Frame

Formats Best Path and Metrics Equal Cost Load Balancing Path Determination Switching Function

CLI Configuration and Addressing Implementing Basic

Addressing Schemes Basic Router

Configuration Building the Routing Table

Introducing the Routing Table

Directly Connected Networks

Static Routing Dynamic Routing Routing Table Principles

Inside the Router Routers are computers Router CPU and Memory Internetwork Operating System Router Bootup Process Router Ports and Interfaces Routers and the Network Layer

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Routers are Computers

A router is a computer: CPU, RAM, ROM, Operating System

The first router: used for the Advanced Research Projects Agency Network (ARPANET): IMP (Interface Message Processor) Honeywell 516 minicomputer that brought the ARPANET to life

on August 30, 1969.

Leonard Kleinrock and the first IMP.

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Routers forwarding packets (packet switching): From the original source to the final destination. Selects best path based on destination IP address

A router connects multiple networks: Interfaces on different IP networks

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Router interfaces: LAN WAN

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Routers Determine the Best Path

The router’s primary responsibility: Determining the best path Forwarding packets toward their destination

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Routers Determine the Best Path

Routing table Determines best path. Best match between destination IP address and network

address in routing table

IP Packet enters router’s Ethernet interface.

Router examines the packet’s destination IP address.

Router searches for a best match between packet’s destination IP address and network address in routing table.

Using the exit-interface in the route, the packet is forwarded to the next router or the final destination.

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Router CPU and Memory

CPU - Executes operating system instructions Random access memory (RAM)

running copy of configuration file routing table ARP cache

Read-only memory (ROM) Diagnostic software used when router is powered up. Router’s bootstrap program Scaled down version of operating system IOS

Non-volatile RAM (NVRAM) Stores startup configuration. (including IP addresses, Routing protocol)

Flash memory - Contains the operating system (Cisco IOS) Interfaces - There exist multiple physical interfaces that are used to connect

network. Examples of interface types: Ethernet / fast Ethernet interfaces Serial interfaces Management interfaces

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Router physical characteristics

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Cisco IOS - Internetwork Operating System

Responsible for managing the hardware and software resources: Allocating memory Managing processes Security Managing file systems

Many different IOS images. An IOS image is a file that contains the entire IOS for that router.

Router model IOS features

Example IPv6 or a routing protocol such as Intermediate System–to–Intermediate System (IS-IS).

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Router Bootup Process (more in later course)

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Bootup Process

running-config

IOS (running)

startup-config IOS

ios (partial)Bootup program

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running-config

IOS (running)

startup-config IOS


Where is the permanent configuration file stored used during boot-up? NVRAM

Where is the diagnostics software stored executed by hardware modules? ROM

Where is the backup (partial) copy of the IOS stored? ROM

Where is IOS permanently stored before it is copied into RAM? FLASH

Where are the bootsystem commands stored which are used to locate the IOS?

NVRAM

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running-config

IOS (running)

startup-config IOS


?

?

?

?

?

?

?

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running-config

IOS (running)

startup-config IOS


startup-config

IOS

Bootup program

ios (partial)

running-config

IOS (running)

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1. ROM 1. POST 2. Bootstrap code executed 3. Check Configuration Register value (NVRAM) 0 = ROM Monitor mode 1 = ROM IOS 2 - 15 = startup-config in NVRAM

2. Check for IOS boot system commands in startup-config file (NVRAM) If boot system commands in startup-config a. Run boot system commands in order they appear in startup-config to locate the IOS b If boot system commands fail, use default fallback sequence to locate the IOS (Flash, TFTP,

ROM)

3. Locate and load IOS, Default fallback sequence: No IOS boot system commands in startup-config a. Flash (sequential) b. TFTP server (netboot) - The router uses the configuration register value to form a filename from

which to boot a default system image stored on a network server. c. ROM (partial IOS) or keep retrying TFTP depending upon router model - If no IOS located, get partial IOS version from ROM

4. Locate and load startup-config configuration a. If startup-config found, copy to running-config b. If startup-config not found, prompt for setup-mode c. If setup-mode bypassed, create a “skeleton” default running-config (no startup-config)

Router Boot Process – Details (later)

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Verify the router boot-up process show version command is used to view information about the

router during the bootup process (later).

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Ports and Interfaces

Port - normally means one of the management ports used for administrative access

Interface normally refers to interfaces that are capable of sending and receiving user traffic.

Note: However, these terms are often used interchangeably in the industry and even with IOS output.

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Management Ports

Console port Terminal PC running terminal emulator software

No need for network access Used for initial configuration

Auxiliary (AUX) port Not all routers have auxiliary ports.

At times, can be used similarly to a console port Can also be used to attach a modem.

Note: Auxiliary ports will not be used in this curriculum.

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Router Interfaces

Interfaces - Receive and forward packets. Various types of networks Different types of media and connectors. Different types of interfaces.

Fast Ethernet interfaces - LANs Serial interfaces - WAN connections including T1, DSL, and ISDN

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Router Interfaces

Router Interface: Different network IP address and subnet mask of that network

Cisco IOS will not allow two active interfaces on the same router to belong to the same network.

FastEthernet 0/0MAC: 0c00-3a44-190a192.168.1.1/24

FastEthernet 0/0MAC: 0c00-41cc-ae1210.1.0.1/16

Serial 0/0172.16.1.1/24

Serial 0/1172.16.1.2/24

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LAN Interfaces

Ethernet and Fast Ethernet interfaces Connects the router to the LAN

Layer 2 MAC address Participates in the Ethernet

Address Resolution Protocol (ARP): Maintains ARP cache for that interface Sends ARP requests when needed Responds with ARP replies when required

Typically an RJ-45 jack (UTP). Router to switch: straight-through cable Router to router: crossover cable

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WAN Interfaces

Point-to-Point, ISDN, and Frame Relay interfaces Connects routers to external networks. The Layer 2 encapsulation can be different types including:

PPP Frame Relay HDLC (High-Level Data Link Control).

Note: MAC addresses are used only on Ethernet interfaces and are not on WAN interfaces.

Layer 2 WAN encapsulation types and addresses are covered in a later course.

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Routers at the Network Layer

Layer 3 device because its primary forwarding decision is based on the information in the Layer 3 IP packet (destination IP address).

This is known as routing.

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Routers Operate at Layers 1, 2, and 3

Path Determination and Switching Functions

Packet Fields and Frame Formats Best Path and Metrics Equal Cost Load Balancing Path Determination Switching Function

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Path Determination and Switching Functions

The following sections focus on exactly what happens to data as it moves from source to destination. Review the packet and frame field specifications Discuss in detail how the frame fields change from hop to hop,

whereas the packet fields remain unchanged

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Ethernet Frame

Layer 2 addresses: Interface-to-Interface on the same network. Changes as packet is decapsulated and encapsulated from

network to network Layer 3 addresses:

Original source layer 3 address (IP) Final destination layer 3 address (IP) Does not change (except with NAT, but this is not a concern of

IP but an internal network process)

IPv4 (Internet Protocol)

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Best Path

Router’s best-path to a network: optimum or “shortest” path

Routing protocol dependent Dynamic routing protocols use their own rules and metrics. A metric is the quantitative value used to measure the distance to a

given route. The best path to a network is the path with the lowest metric. Example, a router will prefer a path that is one hop away over a path

that is two hops away.

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Best Path

1.5 Mbps

1.5 Mbps

Comparing Dynamic Routing Protocols: RIP and OSPF RIP uses hop count

R1 to R3 Fewer links but much slower

OSPF uses bandwidth R1 to R2 to R3 More routers but much faster links

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What happens if a routing table has two or more paths with the same metric to the same destination network? (equal-cost metric)

Router will perform equal-cost load balancing.

Equal Cost Load Balancing

?

?

To reach the 192.168.1.0/24 network it is 2 hops via R2 and 2 hops via R4.

192.168.1.0/24

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Equal-Cost Paths Versus Unequal-Cost Paths

T1

T3

Can a router use multiple paths if the paths (cost, metric) to reach the destination network are not equal?

Yes, if the routers are using the EIGRP routing protocol which supports unequal cost load balancing.

192.168.1.0/24

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Path Forwarding

Packet forwarding involves two functions: Path determination function Switching function

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Path Forwarding

Path determination function is the process of how the router determines which path to use when forwarding a packet.

To determine the best path, the router searches its routing table for a network address that matches the packet’s destination IP address.

One of three path determinations results from this search: Directly connected network Remote network No route determined

Directly connected network

Router receives packet.

Destination IP address matches a network on one of its directly connected networks.

Packet is forwarded out that network.

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Path Forwarding




Remote network


Destination IP address matches a remote network which can only be reached via another router.

Packet is forwarded out that network to the next-hop router.

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Path Forwarding





Destination IP address does NOT match any network in the router’s routing table.

Packet is dropped.

No route determined

Does this mean the network does not exist?

No, only that the router does not know about that network. (later)

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Path Forwarding

Switching function is the process used by a router to: Accept a packet on one interface and Forward it out another interface

A key responsibility of the switching function is to encapsulate packets in the appropriate data-link frame type for the outgoing data link.

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What does a router do with a packet received from one network and destined for another network?

1. Decapsulates the Layer 3 packet by removing the Layer 2 frame header and trailer2. Examines the destination IP address of the IP packet to find the best path in the

routing table3. Encapsulates the Layer 3 packet into a new Layer 2 frame and forwards the frame

out the exit interface

Dest. MAC 0B-31

Source MAC 00-20

Type 800

Trailer

Layer 2 Data Link Frame

Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

Dest. MAC 00-10

Source MAC 0A-10

Type 800

Trailer

Path Forwarding

192.168.1.10

192.168.4.10

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Remember: Encapsulation

Now, let’s do an example…

Destination IP Address

Source IP Address

Other IP fields

Data

Destination Address

Source Address

Type Data Trailer

Layer 3 IP Packet


Current Data Link Address of Host or Router’s exit interface

Next hop Data Link Address of Host or Router’s interface

These change from host to router, router to router, and router to host.

These addresses do not change!

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This is just a summary. The details will be shown next! Now for the details…

Dest. MAC 00-10

Source MAC 0A-10

Type 800

Trailer


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

Dest. MAC 0B-31

Source MAC 00-20

Type 800

TrailerDest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

DataDest. Add FF-FF

Source Add Type 800

Trailer

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From Host X to Router RTA Host X begins by encapsulating the IP packet into a data link frame (in this

case Ethernet) with RTA’s Ethernet 0 interface’s MAC address as the data link destination address.

How does Host X know to forward to packet to RTA and not directly to Host Y? IP Source and IP Destination Addresses are on different networks

How does Host X know or get RTA’s Ethernet address? Checks ARP Table for Default Gateway IP Address and associated

MAC Address. What if it there is not an entry in the ARP Table?

Host X sends an ARP Request and RTA sends an ARP Reply

Dest. MAC 00-10

Source MAC 0A-10

Type 800

Trailer


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

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RTA1. RTA examines Destination MAC address, which matches the E0 MAC address, so it copies in the

frame.2. RTA sees the Type field is 0x800, IP packet in the data field, a packet which needs to be routed.3. RTA strips off the Ethernet frame.RTA looks up the Destination IP Address in its routing table. 192.168.4.0/24 has next-hop-ip address of 192.168.2.2 and an exit-interface of e1. Since the exit interface is on an Ethernet network, RTA must resolve the next-hop-ip address with a

destination MAC address.4. RTA looks up the next-hop-ip address of 192.168.2.2 in its ARP cache. If the entry was not in the ARP cache, the RTA would need to send an ARP request out e1. RTB

would send back an ARP reply, so RTA can update its ARP cache with an entry for 192.168.2.2. 5. Packet is encapsulated into a new data link (Ethernet) frame.

Dest. MAC 0B-31

Source MAC 00-20

Type 800

Trailer


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

RTA Routing TableNetwork Hops Next-hop-ip Exit-interface192.168.1.0/24 0 Dir.Conn. e0192.168.2.0/24 0 Dir.Conn e1192.168.3.0/24 1 192.168.2.2 e1192.168.4.0/24 2 192.168.2.2 e1

RTA ARP CacheIP Address MAC Address192.168.2.2 0B-31

Dest. MAC 00-10

Source MAC 0A-10

Type 800

Trailer

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RTB1. RTB examines Destination MAC address, which matches the E0 MAC address, and copies in the frame.2. RTB sees Type field, 0x800, IP packet in the data field, a packet which needs to be routed.3. RTB strips off the Ethernet frame.RTB looks up the Destination IP Address in its routing table. 192.168.4.0/24 has next-hop-ip address of 192.168.3.2 and an exit-interface of Serial0. Since the exit interface is not an Ethernet network, RTB does not have to resolve the next-hop-ip address

with a destination MAC address. When the interface is a point-to-point serial connection, (like a pipe), RTB encapsulates the IP packet into

the proper data link frame, using the proper serial encapsulation (HDLC, PPP, etc.). The data link destination address is set to a broadcast (there’s only one other end of the pipe).5. Packet is encapsulated into a new data link (serial, PPP) frame and sent out the link.

Dest. Add FF-FF

Source Add Type 800

Trailer


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

RTB Routing TableNetwork Hops Next-hop-ip Exit-interface192.168.1.0/24 1 192.168.2.1 e0192.168.2.0/24 0 Dir.Conn e0192.168.3.0/24 0 Dir.Conn s0192.168.4.0/24 1 192.168.3.2 s0

Dest. MAC 0B-31

Source MAC 00-20

Type 800

Trailer

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RTC1. RTC copies in the data link (serial, PPP) frame.2. RTC sees the Type field is 0x800, IP packet in the data field, a packet which needs to be routed.3. RTC strips off the data link, serial, frame.RTC looks up the Destination IP Address in its routing table. RTC realizes that this Destination IP Address is on the same network as one of its interfaces and it can sent the packet

directly to the destination and not another router. Since the exit interface is on an directly connected Ethernet network, RTC must resolve the destination ip address

with a destination MAC address.2. RTC looks up the destination ip address of 192.168.4.10 in its ARP cache. If the entry was not in the ARP cache, the RTC would need to send an ARP request out e0. Host Y would send back

an ARP reply, so RTC can update its ARP cache with an entry for 192.168.4.10.5. Packet is encapsulated into a new data link (Ethernet) frame and sent out the interface.

Dest. MAC 0B-20

Source MAC 0C-22

Type 800

Trailer


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

RTC ARP CacheIP Address MAC Address192.168.4.10 0B-20

RTC Routing TableNetwork Hops Next-hop-ip Exit-interface192.168.1.0/24 2 192.168.3.1 s0192.168.2.0/24 1 192.168.3.1 s0192.168.3.0/24 0 Dir.Conn s0192.168.4.0/24 0 Dir.Conn e0

Dest. Add FF-FF

Source Add Type 800

Trailer

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Host Y

Layer 2: Data Link Frame1. Host Y examines Destination MAC address, which matches its Ethernet interface MAC address, and

copies in the frame.2. Host Y sees the Type field is 0x800, IP packet in the data field, which needs to be sent to its IP

process.3. Host Y strips off the data link, Ethernet, frame and sends it to its IP process.

Layer 3: IP Packet4. Host Y’s IP process examines the Destination IP Address to make sure it matches its own IP

Address.. If it does not, the packet will be dropped.

5. The packet’s protocol field is examined to see where to send the data portion of this IP packet: TCP, UDP or other?

Layer 4: TCP, UDP or other?


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

Dest. MAC 0B-20

Source MAC 0C-22

Type 800

Trailer

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The summary once again!

Dest. MAC 00-10

Source MAC 0A-10

Type 800

Trailer


Dest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

Data

Layer 3 IP Packet

Dest. MAC 0B-31

Source MAC 00-20

Type 800

TrailerDest. IP 192.168.4.10

Source IP 192.168.1.10

IP fields

DataDest. Add FF-FF

Source Add Type 800

Trailer

CLI Configuration and Addressing

Implementing Basic Addressing Schemes Basic Router Configuration

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Learning IOS: Lab 1.5.2 (Cabrillo College Version)

Networking Lab NetLab Packet Tracer

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Establishing a HyperTerminal session (next week)

Take the following steps to connect a terminal to the console port on the router: Connect the terminal using the RJ-45 to RJ-45 rollover cable and an RJ-45 to DB-9 or

RJ-45 to DB-25 adapter. Configure the terminal or PC terminal emulation software for 9600 baud, 8 data bits,

no parity, 1 stop bit, and no flow control.

Rollover cable

Console port

Com1 or Com2 serial port

Terminal or a PC with terminal emulation software

Router

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Establishing a Terminal session

Important: A console connection is not the same as a network connection!

=

Tera Term HyperTerminal (comes with Windows) Putty

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Terminal ConnectionNo network connection needed Console Port

When do you need to use a console connection to the router?

What software do you need?

What cable and ports do you use?

When there is not a network connection to the router (can’t use telnet).

Tera Term, HyperTerminal, Putty, etc.

PC: Serial port & Router: Console PortRollover or Console Cable

Serial

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C:\> telnet

C:\> ping

Ethernet ConnectionNetwork connection needed

When can you use a network connection to the router?

What software/command do you need?

What cable and ports do you use?

When should you not use a network connection to configure the router?

When there is a network connection to the router (telnet).

TCP/IP, Terminal prompt (DOS), Tera Term, etc.

PC & Router: Ethernet NICEthernet straight-through cable

When the change may disconnect the telnet connection.

NIC

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Terminal ConnectionNo network connection needed Console Port

C:\> telnet

C:\> ping

Ethernet ConnectionNetwork connection needed

Serial

NIC

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NetLab

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NetLabBasic Router Pod

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Your Interfaces may differ

R1# show ip interface briefInterface IP-Address OK? Method Status

Protocol

FastEthernet0/0 192.168.1.1 YES manual up up

FastEthernet0/1 192.168.1.2 YES manual up up

Serial0/0 192.168.2.1 YES manual up up

Serial0/1 unassigned YES manual up up

FastEthernet 0 = FastEthernet 0/0

FastEthernet 1 = FastEthernet 0/1 = FastEthernet 1/0

Serial 0 = Serial 0/0 = Serial 0/0/0

Serial 1 = Serial 0/1 = Serial 0/0/1

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Learning IOS: Lab 1.5.2 (Cabrillo College Version)

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Command Overview (partial list from lab)Router> user mode

Router> enable

Router# privilege mode

Router# configure terminal

Router(config)# exit

Router# config t

Router(config)# hostname name

Router(config)# enable secret password privilege passwordRouter(config)# line console 0 console passwordRouter(config-line)# password passwordRouter(config-line)# loginRouter(config)# line vty 0 4 telnet passwordRouter(config-line)# password passwordRouter(config-line)# login

Router(config)# banner motd # message # banner

Router(config)# interface type number configure interface

Router(config-if)# ip address address mask

Router(config-if)# description description

Router(config-if)# no shutdown

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Other Commands

Router# copy running-config startup-config

Router# show running-config

Router# show ip route

Router# show ip interface brief

Router# show interfaces

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Different Modes

IOS commands must be entered in the correct mode.

Router# hostname R1

^

% Invalid input detected at '^' marker.

Router# configure terminal

Router(config)# hostname R1

R1(config)#

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Serial Connectors

2500 have the “older,” larger serial interfaces Later Cisco routers use the smart serial interfaces which allows

more data to be forwarded across fewer cable pins.

Smart Serial

“Older” Serial

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Serial Connectors

Router is typically a DTE device. The DTE cable is connected to the serial interface on the router to a

CSU/DSU device (DCE).

DTE Cable

DCE Cable

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WAN Interface Configuration

R1(config)# interface Serial0/0

R1(config-if)# ip address 192.168.2.1 255.255.255.0

R1(config-if)# description Link to R2

R1(config-if)# clock rate 64000 DCE Only

R1(config-if)# no shutdown

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Unsolicited Messages from IOS

The IOS often sends unsolicited messages Does not affect the command Can cause you to lose your place when typing.

R1(config)# interface fastethernet0/0



R1(config-if)# descri

*Mar 1 01:16:08.212: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up

*Mar 1 01:16:09.214: %LINEPROTO-5-UPDOWN: Line protocol on Interface

FastEthernet0/0, changed state to upption

R1(config-if)#

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Unsolicited Messages from IOS

To keep the unsolicited output separate from your input, enter line configuration mode for the console port and add the logging synchronous

R1(config)# line console 0

R1(config-line)# logging synchronous

R1(config-if)# descri

*Mar 1 01:28:04.242: %LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up

*Mar 1 01:28:05.243: %LINEPROTO-5-UPDOWN: Line protocol on Interface

FastEthernet0/0, changed state to up

R1(config-if)# description

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LAN Interface Configuration

R1(config)# interface FastEthernet0/0


R1(config-if)# description R1 LAN


Fa0/1

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Each Interface Belongs to a Different Network

R1(config)# interface FastEthernet0/1R1(config-if)# ip address 192.168.1.2 255.255.255.0192.168.1.0 overlaps with FastEthernet0/0R1(config-if)# no shutdown192.168.1.0 overlaps with FastEthernet0/0FastEthernet0/1: incorrect IP address assignment

Fa0/1192.168.1.1/24

192.168.1.2/24

Same Network!

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Each Interface Belongs to a Different Network

R1# show ip interface briefInterface IP-Address OK? Method Status

ProtocolFastEthernet0/0 192.168.1.1 YES manual up upSerial0/0 192.168.2.1 YES manual up upFastEthernet0/1 192.168.1.2 YES manual administratively down downSerial0/1 unassigned YES unset administratively down down

Fa0/1

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Verifying InterfacesR1# show interfaces<some interfaces not shown>FastEthernet0/0 is up, line protocol is up (connected) Hardware is Lance, address is 0007.eca7.1511 (bia 00e0.f7e4.e47e) Description: R1 LAN Internet address is 192.168.1.1/24 MTU 1500 bytes, BW 100000 Kbit, DLY 100 usec, rely 255/255, load 1/255 Encapsulation ARPA, loopback not set ARP type: ARPA, ARP Timeout 04:00:00, Last input 00:00:08, output 00:00:05, output hang never Last clearing of “show interface” counters never Queueing strategy: fifo Output queue :0/40 (size/max) 5 minute input rate 0 bits/sec, 0 packets/sec 5 minute output rate 0 bits/sec, 0 packets/sec 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants, 0 throttles<output omitted>Serial0/0 is up, line protocol is up (connected) Hardware is HD64570 Description: Link to R2 Internet address is 192.168.2.1/24 MTU 1500 bytes, BW 1544 Kbit, DLY 20000 usec, rely 255/255, load 1/255 Encapsulation HDLC, loopback not set, keepalive set (10 sec) Last input never, output never, output hang never<output omitted>

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Verify Router ConfigurationR1# show running-config!version 12.3!hostname R1!interface FastEthernet0/0description R1 LANip address 192.168.1.1 255.255.255.0!interface Serial0/0description Link to R2ip address 192.168.2.1 255.255.255.0clock rate 64000!banner motd ^C******************************************WARNING!! Unauthorized Access Prohibited!!******************************************^C!line con 0password ciscologinline vty 0 4password ciscologin!end

Note: shutdown is the default. no shutdown does not show in the configuration.

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Save ConfigurationR1# copy running-config startup-configR1# show startup-configUsing 728 bytes!version 12.3!hostname R1!interface FastEthernet0/0description R1 LANip address 192.168.1.1 255.255.255.0!interface Serial0/0description Link to R2ip address 192.168.2.1 255.255.255.0clock rate 64000!banner motd ^C******************************************WARNING!! Unauthorized Access Prohibited!!******************************************^Cline con 0password ciscologinline vty 0 4password ciscologin!end

Building the Routing Table

Introducing the Routing Table Directly Connected Networks

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Show Routing TableR1# show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area* - candidate default, U - per-user static route, o - ODRP - periodic downloaded static route

Gateway of last resort is not set

C 192.168.1.0/24 is directly connected, FastEthernet0/0C 192.168.2.0/24 is directly connected, Serial0/0

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Routing table is a data file in RAM that is used to store route information about: Directly connected networks Remote networks

R1# show ip route

Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGPD - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter areaN1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, ia - IS-IS inter area* - candidate default, U - per-user static route, o - ODRP - periodic downloaded static route

Gateway of last resort is not set


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Directly connected interfaces contain the exit interface (more later)

R1# show ip route

<output omitted>


Exit Interfaces

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directly connected network is a network that is directly attached to one of the router interfaces.

When a router’s interface is configured with an IP address and subnet mask, the interface becomes a host on that attached network.

Active directly connected networks are added to the routing table.

R1# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<output omitted>


Directly Connected Networks

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A remote network is a network that is not directly connected to the router.

A remote network is a network that can only be reached by sending the packet to another router.

Remote networks are added to the routing table using: (later) Dynamic routing protocol Static routes

R1# show ip routeCodes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP<output omitted>


Remote Network

Chapter 1Introduction to Routing and Packet Forwarding

CIS 82 Routing Protocols and Concepts

Rick Graziani

Cabrillo College

[email protected]

Documents

Chapter 1 Introduction to Routing and Packet Forwarding CIS 82 Routing Protocols and Concepts Rick Graziani Cabrillo College [email protected] Last