From Mycomputer Notes

All CLI configuration changes to a Cisco router are made from global configuration mode, which is sometimes called global config. Global config is the primary configuration mode.

Contents 1 Configuring a Router 1.1 Configuring router passwords 1.1.1 Console Password 1.1.2 Virtual Terminal Password 1.1.3 Enable Password 1.1.4 Password encryption 1.2 Configuring Serial & Ethernet Interfaces

Configuring a Router

A router should be given a unique name as one of the first configuration tasks In order to accomplished this go to the global configuration mode with the following command:

Router(config)#hostname Tokyo Tokyo(config)#

Configuring router passwords

As a best practive restrict access to routers with a password. Passwords should always be configured for virtual terminal (vty) lines and the console line. Passwords are also used to control access to privileged EXEC mode so that only authorized users may make changes to the configuration file.

Console Password

Router(Config)# line console 0
Router(Config)# password cisco
Router(Config)# login

Virtual Terminal Password

Router(Config)# line vty 0 4 (when configuring telenet sessions)
Router(Config)# password cisco
Router(Config)# login

Enable Password

Router(Config)# enable password SanFranciso
Router(Config)# service password-encryption (to encrypt non  encrypted passwords)

The enable password used to restrict access to the privileged EXEC mode IF the enable secret has not been set.

Sometimes it is undesirable for passwords to be shown in clear text in the output from the show running-config or show startup-config commands and a a best practice we should used the "service password-encryption" command

Password encryption

Router(Config)# enable secret <password> (encrypted password)

The enable secret commands is used to restrict access to the privileged EXEC mode The enable secret command should be used because the enable secret command is encrypted

Configuring Serial & Ethernet Interfaces

To configure a serial interface either from the console or through a virtual terminal line follow these steps:

1. Enter global configuration mode
2. Enter interface mode.
3. Specify the interface address and subnet mask.
4. Set clock rate if a DCE cable is connected. Skip this step if a DTE cable is connected.
5. Turn on the interface.

The variable "TYPE" here is for serial, ethernet, fasethernet, token ring and others.

Router(Config)# interface type port
Router(Config)# interface type slot/port

Each Interface that has been configured with the above commands needs an IP Address and a Subnet mask. Configure the IP address with the following commands:

Router(config)#interface serial 0/0 Router(config-if)#ip address <ip address > <netmask >

Serial interfaces require a clock signal to control the timing of the communications in most cases a DCE device such as a CSU/DSU will provide the clock. By default, Cisco routers are DTE devices but they can be configured as DCE devices.

The clock is enabled and speed is specified with the clock rate command. Available clock rates are:

• 1200
• 2400
• 9600
• 19200
• 38400
• 56000
• 64000
• 72000

Some bit rates might not be available on certain serial interfaces. This depends on the capacity of each interface.

This commands is used to administratively turn off a interface

Router(Config)#shutdown