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Basic Router Configuration

The first prompt appears at user mode. User mode allows you to view the state of the router, but does not allow you to modify its configuration. Do not confuse the term "user" as used in user mode with users of the network. User mode is intended for the network technicians, operators, and engineers who have the responsibility to configure network devices.

Router>

The enable command is used to enter the privileged EXEC mode. This mode allows the user to make configuration changes on the router. The router prompt will change from a ">" to a "#" in this mode.

Router>enable
Router#

Hostnames and Passwords

The figure shows the basic router configuration command syntax used to configure R1 in the following example. You can open Packet Tracer Activity 1.2.2 and follow along or wait until the end of this section to open it.

First, enter the global configuration mode.

Router#config t

Next, apply a unique (term used mainly for convenience and further documentation routines by Cisco) hostname to the router.

Router(config)#hostname R1
R1(config)#

Now, configure a password that is to be used to enter privileged EXEC mode. In production environments, routers should have strong passwords. See the links at the end of this section for more information on creating and using strong passwords.

Router(config)#enable secret class

Next, configure the console and Telnet lines with the password cisco. Once again, the password cisco is used only in our lab environment. The command login enables password checking on the line. If you do not enter the command login on the console line, the user will be granted access to the line without entering a password.

R1(config)#line console 0
R1(config-line)#password cisco
R1(config-line)#login
R1(config-line)#exit
R1(config)#line vty 0 4
R1(config-line)#password cisco
R1(config-line)#login
R1(config-line)#exit

Configuring a Banner

From the global configuration mode, configure the message-of-the-day (motd) banner. A delimiting character, such as a "#" is used at the beginning and at the end of the message. The delimiter allows you to configure a multiline banner, as shown here.

R1(config)#banner motd #
Enter TEXT message. End with the character '#'.
******************************************
WARNING!! Unauthorized Access Prohibited!!
******************************************
#

Configuring an appropriate banner is part of a good security plan. At a very minimum, a banner should warn against unauthorized access. Never configure a banner that "welcomes" an unauthorized user.

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Router Interface Configuration

You will now configure the individual router interfaces with IP addresses and other information. First, enter the interface configuration mode by specifying the interface type and number. Next, configure the IP address and subnet mask:

R1(config)#interface Serial0/0/0
R1(config-if)#ip address 192.168.2.1 255.255.255.0

It is good practice to configure a description on each interface to help document the network information. The description text is limited to 240 characters. On production networks a description can be helpful in troubleshooting by providing information about the type of network that the interface is connected to and if there are any other routers on that network. If the interface connects to an ISP or service carrier, it is helpful to enter the third party connection and contact information;

R1(config-if)#description Link to R2

After configuring the IP address and description, the interface must be activated with the no shutdown command. This is similar to powering on the interface. The interface must also be connected to another device (a hub, a switch, another router, etc.) for the Physical layer to be active.

Router(config-if)#no shutdown

Note: When cabling a point-to-point serial link in our lab environment, one end of the cable is marked DTE and the other end is marked DCE. The router that has the DCE end of the cable connected to its serial interface will need the additional clock rate command configured on that serial interface.

R1(config-if)#clock rate 64000

Repeat the interface configuration commands on all other interfaces that need to be configured.