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Semester 2 Module 3 Configuring a Router

Yuda college of business

James Chen

ydjames@ydu.edu.tw

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Outline

Configuring a Router Finishing the Configuration

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CLI command modes

All command-line interface (CLI) configuration changes to a Cisco router are made from the global configuration mode.

Other more specific modes are entered depending upon the configuration change that is required, but these specific modes are all subsets of the global configuration mode.

Note: The prompt changes to indicate that the router is now in global configuration mode.

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These are just a few of the modes that can be entered from global configuration mode: Interface mode Line mode Router mode Subinterface mode Controller mode

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Typing exit from one of these specific configuration modes will return the router to global configuration mode.

Pressing Ctrl-Z leaves the configuration modes completely and returns the router to privileged EXEC mode.

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Configuring a router name

A router should be given a unique name as one of the first configuration tasks.

This task is accomplished in global configuration mode using the following commands:

Router(config)#hostname TokyoTokyo(config)#

As soon as the Enter key is pressed, the prompt changes from the default host name (Router) to the newly configured host name, which is Tokyo in the example.

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Configuring router passwords

Passwords virtual terminal lines console line privileged EXEC mode

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The following commands are used to set an optional but recommended password on the console line:

Router(config)#line console 0

Router(config-line)#password <password>

Router(config-line)#login

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The following commands are used to set the password on the VTY lines:

Router(config)#line vty 0 4

Router(config-line)#password <password>

Router(config-line)#login

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The enable password and the enable secret are used to restrict access to the privileged EXEC mode.

The enable password is only used if the enable secret has not been set.

It is recommended that the enable secret always be set and used because it is encrypted while the enable password is not encrypted.

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These are the commands that are used to set the enable passwords:

Router(config)#enable password <password>

Router(config)#enable secret <password>

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This command is used to encrypt passwords in configuration output:

Router(config)#service password-encryption

The service password-encryption command applies a weak encryption to all unencrypted passwords.

The enable secret <password> command uses a strong MD5 algorithm for encryption.

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Examining the show commands

There are many show commands that can be used to examine the contents of files in the router and for troubleshooting.

In both privileged EXEC and user EXEC modes, the command show ? provides a list of available show commands.

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show interfaces – Displays all the statistics for all the interfaces on the router. To view the statistics for a specific interface, enter the show interfaces command followed by the specific interface and port number. For example:

Router#show interfaces serial 0/1 show controllers serial – Displays information-

specific to the interface hardware show clock – Shows the time set in the router show hosts – Displays a cached list of host names

and addresses show users – Displays all users who are connected

to the router

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show history – Displays a history of commands that have been entered

show flash – Displays information about flash memory and what IOS files are stored there

show version – Displays information about the router and the IOS that is running in RAM

show ARP – Displays the ARP table of the router show protocol – Displays the global and interface specific

status of any configured Layer 3 protocols show startup-configuration – Displays the saved configuration

located in NVRAM show running-configuration – Displays the configuration

currently running in RAM

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Configuring a serial interface

To configure a serial interface follow these steps: Enter global configuration mode Enter interface mode Specify the interface address and subnet mask Set clock rate if a DCE cable is connected. Skip

this step if a DTE cable is connected. Turn on the interface

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Configure the IP address using the following commands:

Enter global configure terminal configuration mode by entering the command.

Router(config)#interface serial 0/0

Router(config-if)#ip address <ip address> <netmask>

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Serial interfaces require a clock signal to control the timing of the communications.

In most environments, a DCE device such as a CSU will provide the clock.

By default, Cisco routers are DTE devices but they can be configured as DCE devices.

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The clock is enabled and speed is specified with the clock rate command.

The available clock rates in bits per second are: 1200, 2400, 9600, 19200, 38400, 56000, 64000, 72000, 125000, 148000, 500000, 800000, 1000000, 1300000, 2000000, or 4000000.

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By default, interfaces are turned off, or disabled.

To turn on or enable an interface, the command no shutdown is entered

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The commands for setting a clock rate and enabling a serial interface are as follows:

Router(config)#interface serial 0/0

Router(config-if)#clock rate 56000

Router(config-if)#no shutdown

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Executing adds, moves, and changes

If a configuration requires modification, go to the appropriate mode and enter the proper command.

To verify changes, use the show running-config command.

To save the configuration variables to the startup configuration file in NVRAM, enter the following command at the privileged EXEC prompt:

Router#copy running-config startup-config

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Configuring an Ethernet interface

To configure an Ethernet interface follow these steps: Enter global configuration mode Enter interface configuration mode Specify the interface address and subnet mask Enable the interface

By default, interfaces are turned off, or disabled. To turn on or enable an interface, the command no

shutdown is entered.

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Outline

Configuring a Router Finishing the Configuration

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Importance of configuration standards

It is important for standards to be developed for configuration files within an organization.

This allows control of the number of configuration files that must be maintained, how the files are stored, and where the files are stored.

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A standard is a set of rules or procedures that are either widely used or officially specified.

Without standards in an organization, a network could be in chaos should an interruption in service occur.

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Interface descriptions

A description of an interface can help a network user remember specific information about the interface, such as what network the interface services.

The description is meant solely as a comment about the interface.

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Configuring interface description Procedure steps:

Enter global configure terminal configuration mode by entering the command.

Enter specific interface mode (for example interface Ethernet 0) interface ethernet 0.

Enter the command description followed by the information that is to be displayed. For example, XYZ Network, Building 18.

Exit interface mode back to privileged EXEC mode by using the command ctrl-Z.

Save the configuration changes to NVRAM by using the command copy running-config startup-config.

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Login banners

A login banner is a message that is displayed at login and is useful for conveying messages that affect all network users, such as notices of impending system shutdowns.

Login banners can be seen by anyone. Therefore, careful attention should be used in the

wording of a banner message. “Welcome” is an invitation for anyone to enter a router and is probably not an appropriate message.

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Configuring message-of-the-day (MOTD) A message-of-the-day (MOTD) banner can be

displayed on all connected terminals. Enter global configuration mode to configure a

message-of-the-day (MOTD) banner. Use the banner motd command, followed by a

space and a delimiting character, such as the pound sign (#).

Add a message-of-the-day (MOTD) followed by a space and the delimiting character again.

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Follow these steps to create and display a message-of-the-day:

1. Enter global configuration mode by using the command configure terminal.

2. Enter the command banner motd # The message of the day goes here #.

3. Save changes by issuing the command copy running-config startup-config.

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Host name resolution

Host name resolution is the process that a computer system uses to associate a host name with an IP address.

A list of host names and their associated IP addresses is called a host table.

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Configuring host tables

The procedure to configure the host table: 1. Enter global configuration mode in the router. 2. Enter the command ip host followed by the

name of the router and all IP addresses associated with the interfaces on each router.

3. Continue entering until all routers in the network are entered.

4. Save the configuration to NVRAM.

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Configuration backup and documentation

Management of device configuration includes the following tasks: Listing and comparing configuration files on running

devices Storage of configuration files on network servers Performing software installations and upgrades

Configuration files should be stored as backup files in the event of a problem.

Configuration files can be stored on a network server, on a TFTP server, or on a disk stored in a safe place.

Documentation should be included with this offline information.

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Copying, editing, and pasting configurations

The copy running-config tftp command can be used to store the current configuration on a network TFTP server.

To do so, complete the following tasks: Step 1 Enter the copy running-config tftp command. Step 2 Enter the IP address of the host where the

configuration file will be stored. Step 3 Enter the name to assign to the configuration file. Step 4 Confirm the choices by answering yes each time.

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A configuration file stored on one of the network servers can be used to configure a router.

To do so, complete the following tasks: Enter configuration mode by entering the copy tftp

running-config command At the system prompt, select a host or network

configuration file. At the system prompt, enter the name of the configuration

file or accept the default name.

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