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CIS 81 Fundamentals of NetworkingChapter 2: Configuring a Network
Operating System
Rick Graziani
Cabrillo College
Fall 2013
Chapter 2 - Objectives
Explain the purpose of Cisco IOS.Explain how to access and navigate Cisco IOS to configure
network devices.Describe the command structure of Cisco IOS software.Configure hostnames on a Cisco IOS device using the CLI.Use Cisco IOS commands to limit access to device
configurations.Use Cisco IOS commands to save the running
configuration.Explain how devices communicate across network media.Configure a host device with an IP address.Verify connectivity between two end devices.
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Cisco IOSOperating Systems
All networking equipment depend on operating systems: End users (PCs, laptops, smart phones, tablets) Switches Routers Wireless access points Firewalls
Cisco Internetwork Operating System (IOS) Collection of network operating systems used on Cisco devices
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Cisco IOS
Operating Systems
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Cisco IOS
Purpose of OS
PC operating systems (Windows 8, Linux & OS X) perform technical functions that enable • Use of a input and output devices• Manage processes and programs• Manage file systems, security, hardware, etc.
Switch or router IOS provides options to • Same functions as host operating systems• Configure interfaces• Enable routing and switching functions
All networking devices come with a default IOS (switches, routers, firewalls)
Possible to upgrade the IOS version or feature set 5
Cisco IOS
Location of the Cisco IOS
IOS stored in Flash Non-volatile storage – not lost when power is lost Can be changed or overwritten as needed Can be used to store multiple versions of IOS IOS copied from flash to volatile RAM when booted Quantity of flash and RAM memory determines IOS that
can be used 6
Cisco IOS
IOS FunctionsMajor functions performed or enabled by Cisco routers and switches include:
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Router/Switch 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
ios (partial)Bootup program
Where is the permanent configuration file stored used during boot-up? NVRAM (B)
Where is the diagnostics software stored executed by hardware modules? ROM (D)
Where is the backup (partial) copy of the IOS stored? ROM (D)
Where is IOS permanently stored before it is copied into RAM? FLASH (C)
Where are all changes to the configuration immediately stored? RAM (A)
A B C D
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running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
?
?
?
?
?
?
?
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running-config
IOS (running)
startup-config IOS
ios (partial)Bootup program
startup-config
IOS
Bootup program
ios (partial)
running-config
IOS (running)
A B C D
B A D
C D A
Cisco IOS
CCO Account Benefits and IOS Files
This video introduces Cisco Connection Online (CCO). CCO has a wealth of information available regarding Cisco products and services. 13
Accessing a Cisco IOS DeviceConsole Access Method
Most common methods to access the Command Line Interface Console Telnet or SSH AUX port
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Accessing a Cisco IOS Device
Console Access Method
Console portDevice is accessible even if no networking services have been configured (out-of-band)Need a special console cable (aka rollover cable)Allows configuration commands to be enteredShould be configured with passwords to prevent unauthorized accessDevice should be located in a secure room so console port can not be easily accessed
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Establishing a HyperTerminal session (next week)
Connect PC using the RJ-45/mini-USB to Serial/USB rollover cable. Configure the terminal or PC terminal emulation software for:
9600 baud 8 data bits no parity 1 stop bit no flow control
Rollover cable
Console port
Com1 or Com2 serial port Or USB port with USB-to-Serial adapter
Terminal or a PC with terminal emulation software
Router
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Terminal (Serial) Settings)
Configure the terminal or PC terminal emulation software for: 9600 baud 8 data bits no parity 1 stop bit no flow control.
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Establishing a Terminal/Serial/Console session
Important: A console connection is not the same as a network connection!
=
• PuTTY• Tera Term• SecureCRT• HyperTerminal• OS X Terminal• Zoc
Dumb Terminal
Accessing a Cisco IOS Device
Telnet, SSH, and AUX Access MethodsTelnet Method for remotely accessing the CLI over a network Require active networking services and one active interface that
is configured
Secure Shell (SSH) – Preferred over Telnet Remote login similar to Telnet but utilizes more security Stronger password authentication Uses encryption when transporting data
Aux Port (not used too much) Out-of-band connection Uses telephone line Can be used like console port
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C:\> ssh
C:\> ping
Ethernet ConnectionNetwork connection needed
When can you use a network connection to connect 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
Accessing a Cisco IOS Device
Terminal Emulation Programs
Software available for connecting to a networking device (usually same as terminal/serial/console connection):PuTTYTera TermSecureCRTHyperTerminalOS X TerminalZoc
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Navigating the IOSCisco IOS Modes of Operation
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Navigating the IOS
Cisco IOS Modes of Operation
enable
configure terminal
interface < >router < >line < >
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Navigating the IOS
Primary Modes
enableenable
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Navigating the IOS
Global Configuration Mode and Submodes
Global configuration mode and interface configuration modes can only be reached from the privileged EXEC mode. 25
Navigating the IOS
Navigating between IOS Modes
Similar IOS commands for switches and routers26
Navigating the IOS
Navigating between IOS Modes (cont.)Switch> user mode
Switch> enable go to privilege mode
Switch# configure terminal go to global configuration mode
Switch(config)# interface vlan 1 go to interface mode
Switch(config-if)# exit
Switch(config)# exit
Switch# config t Shortened commands and parameters
Switch(config)# vlan 1 go to VLAN configuration mode
Switch(config-vlan)# end go to privilege-EXEC mode
Switch# disable
Switch> enable
Switch# config t
Switch(config)# line vty 0 4 go to interface (line) mode
Switch(config-line)# exit
Switch(config)#
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Common Commands for Switches and RoutersSwitch> user mode
Switch> enable
Switch# privilege mode
Switch# configure terminal
Switch(config)# exit
Switch# config t
Switch(config)# hostname name
Switch(config)# enable secret password privilege passwordSwitch(config)# line console 0 console passwordSwitch(config-line)# password passwordSwitch(config-line)# loginSwitch(config)# line vty 0 4 telnet passwordSwitch(config-line)# password passwordSwitch(config-line)# login
Switch(config)# banner motd # message # banner
Switch(config)# interface type number configure interface
Switch(config-if)# description description
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Making your life easier!
Switch# enableSwitch(config)# line console 0 Console portSwitch(config-line)# logging synchronous IOS will notSwitch(config-line)# exec-timeout 0 0 passwordSwitch(config)# no ip domain-lookup passwordSwitch(config-line)# login
Switch(config)# banner motd # message # banner
Switch(config)# interface type number configure interface
Switch(config-if)# description description
Navigating the IOS
Navigating between IOS Modes
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The Command StructureIOS Command Structure
31
The Command Structure
Cisco IOS Command Reference
IOS Command Conventions
The general syntax for a command is the command followed by any appropriate keywords (defined) and arguments (undefined).
An argument is generally not a predefined word.
An argument is a value or variable defined by the user.
Switch(config-if)# description string
Boldface text indicates commands and keywords that are typed as shown Italic text indicates an argument for which you supply the value. For the description command, the argument is a string value. The string value can be any text string of up to 80 characters.Example:
Switch(config-if)# description MainHQ Office Switch
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The Command Structure
Cisco IOS Command Reference For the ping command:
Switch> ping IP-address
Switch> ping 10.10.10.5
The command is ping and the user defined argument is the 10.10.10.5.
Similarly, the syntax for entering the traceroute command is:
Switch> traceroute IP-address
Switch> traceroute 192.168.254.254
The command is traceroute and the user defined argument is the 192.168.254.254.
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The Command Structure
Context Sensitive Help
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The Command Structure
Command Syntax Check
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The Command Structure
Command Syntax Check
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The Command Structure
Command Syntax Check
37
The Command Structure
Hot Keys and Shortcuts Tab - Completes the remainder of a partially typed command or
keyword Ctrl-R - Redisplays a line Ctrl-A – Moves cursor to the beginning of the line Ctrl-Z - Exits configuration mode and returns to user EXEC Down Arrow - Allows the user to scroll forward through former
commands Up Arrow - Allows the user to scroll backward through former
commands Ctrl-Shift-6 - Allows the user to interrupt an IOS process such
as ping or traceroute. Ctrl-C - Aborts the current command and exits the configuration
mode
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The Command Structure
IOS Examination Commands
39
The Command Structure
The show version Command
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The Command Structure
Navigating the IOS
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HostnamesWhy the Switch
Let’s focus on Creating a two PC network connected via a switchSetting a name for the switchLimiting access to the device configurationConfiguring banner messages Saving the configuration
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Hostnames
Device NamesHostnames allow devices to be identified by network administrators over a network or the Internet.
Some guidelines for naming conventions are that names should:Start with a letterContain no spacesEnd with a letter or digitUse only letters, digits, and dashesBe less than 64 characters in length
Without names, network devices are difficult to identify for configuration purposes.
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Hostnames
Configuring Hostnames
Switch(config)# hostname Sw-Floor-3
Sw-Floor3(config)#
Switch(config)# hostname Sw-Floor-2
Sw-Floor2(config)#
Switch(config)# hostname Sw-Floor-1
Sw-Floor1(config)#
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Limiting Access to Device ConfigurationsSecuring Device Access
The passwords introduced here are:
Enable password - Limits access to the privileged EXEC mode
Enable secret - Encrypted, limits access to the privileged EXEC mode
Console password - Limits device access using the console connection
VTY password - Limits device access over Telnet
Note: In most of the labs in this course, we will be using simple passwords such as cisco or class.
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Limiting Access to Device Configurations
Securing Privileged EXEC Access
use the enable secret command, not the older enable password command
enable secret provides greater security because the password is encrypted
class
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Limiting Access to Device Configurations
Securing User EXEC Access
Console port must be secured• reduces the chance of unauthorized personnel physically
plugging a cable into the device and gaining device access
vty lines allow access to a Cisco device via Telnet• number of vty lines supported varies with the type of
device and the IOS version47
Limiting Access to Device Configurations
Encrypting Password Display
service password-encryptionprevents passwords from showing up as plain text when viewing the configuration purpose of this command is to keep unauthorized individuals from viewing passwords in the configuration fileonce applied, removing the encryption service does not reverse the encryption
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Limiting Access to Device Configurations
Banner Messages
Important part of the legal process in the event that someone is prosecuted for breaking into a device
Wording that implies that a login is "welcome" or "invited" is not appropriate
Switch(config)# banner motd # This is a secure system Authorized Access Only!!! #
Sw-Floor3(config)#
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Saving Configurations
Configuration FilesSwitch# show running-config
Switch# copy running-config startup-config
<Changes made>
Switch# delete vlan.dat
Delete filename [vlan.dat]?
Delete flash:vlan.dat? [confirm]
Switch# erase startup-config
Switch# reload
System configuration has been modified. Save? [yes/no]: n
Proceed with reload? [confirm]
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Saving Configurations
Capturing Text
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Saving Configurations
Capturing Text
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Ports and AddressesIP Addressing in the Large Each end device on a
network must be configured with an IP address
Structure of an IPv4 address is called dotted decimal
IP address displayed in decimal notation, with four decimal numbers between 0 and 255
With the IP address, a subnet mask is also necessary
IP addresses can be assigned to both physical ports and virtual interfaces
IPv4 and IPv6 addresses will be discussed in more detail later 53
Ports and Addresses
Interfaces and Ports Terms are used interchangeably Some interfaces can be can be configured with an IP address such as:
NIC (Ethernet interface) on a host/computer Router’s Ethernet or Serial interfaces
Switches have ports (interfaces) but do not typically have IP addresses assigned to them
Used to connect devices on LANs that do have IP addresses such as hosts, routers, printers.
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Addressing Devices
Configuring a Switch Virtual Interface
Allows the network administrator to communicate (SSH, telnet, ping) with the switch.
It is OPTIONAL “Layer 2” switches do NOT need an IP address to forward Ethernet frames. IP address - together with subnet mask, uniquely identifies end device on
internetwork (more later) Subnet mask - determines which part of a larger network is used by an IP address
interface VLAN 1 - interface configuration mode ip address 192.168.10.2 255.255.255.0 - configures the IP address and subnet
mask for the switch no shutdown - administratively enables the interface Switch still needs to have physical ports configured and VTY lines to enable
remote management 55
Addressing Devices
Manual IP Address Configuration for End Devices
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More later!
Addressing Devices
Automatic IP Address Configuration for End Devices
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More later!
Addressing Devices
IP Address Conflicts
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More later!
In Class Lab
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Verifying ConnectivityTest the Loopback Address on an End Device
C:\> ping 127.0.0.1
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128 60
Verifying Connectivity
Testing the Interface Assignment
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Verifying Connectivity
Testing End-to-End Connectivity
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Configuring a Network Operating System
Chapter 2 Summary
Services provided by the Cisco IOS accessed using a command-line interface (CLI)• accessed by either the console port, the AUX port, or through
telnet or SSH• can make configuration changes to Cisco IOS devices• a network technician must navigate through various hierarchical
modes of the IOS Cisco IOS routers and switches support a similar operating system Introduced the initial settings of a Cisco IOS switch device
• setting a name• limiting access to the device configuration• configuring banner messages • saving the configuration
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DEMO
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In Class Lab
CIS 81 Fundamentals of NetworkingChapter 2: Configuring a Network
Operating System
Rick Graziani
Cabrillo College
Fall 2013