Initial Configuration of a Cisco Router

The first time a Cisco router is powered on, the startup configuration file is blank, so it will boot into the initial configuration dialog. This dialog is designed to walk a novice through the basic steps and requirements of configuring a Cisco router.

The initial configuration dialog is a menu-driven command-and-response query designed to configure a router with a bare-bones configuration. The dialog will start anytime a configuration file is not found in NVRAM during the boot sequence, as described previously. The two instances in which a configuration file will not exist in NVRAM are when the router is powered on for the first time and when the router is reloaded subsequent to the startup configuration file being erased.

The following code is a sample initial router configuration phase:

 Would you like to enter the initial configuration dialog? [yes] <Return> First, would you like to see the current interface summary? [yes] <Return> Any interface listed with OK? Value "NO" does not have a valid configuration Interface    IP-Address   OK?   Method    Status   Protocol Serial 0     unassigned   NO    not set   up       down Serial 1     unassigned   NO    not set   up       down Ethernet 1   unassigned   NO    not set   up       down Ethernet 2   unassigned   NO    not set   up       down Configuring global parameters: 

Notice that in the configuration dialog, many of the questions have answers in brackets following them. These are the default values or answers for the questions. To accept a default value, simply press Enter and move on to the next question. If you don't want to use the default value, simply enter your own. Also, if at any time you are stumped as to the proper syntax to use, you can always type ? at the prompt for help or press the Tab key, which will finish your syntax for you.

The preceding interface summary indicates that the router has two serial and two Ethernet interfaces. In this example, we will configure both serial interfaces and neither of the Ethernet interfaces. None of the four interfaces has been assigned an IP address, which is indicated by the "unassigned" designation, listed under the IP-Address column. The status of the interface is set to "up" because this is the default value. We must manually shut down the interface to turn it off. However, the protocol is listed as "down" because no active connections are on the interface. After the interface summary is displayed, the next step in the initial configuration dialog is to configure the hostname, passwords, routing protocols, and IP addressing, as shown here:

 Enter host name [Router] NFLD The enable secret is a one-way cryptographic secret used instead  of the enable password when it exists. Enter enable secret: NFLD The enable password is used when no enable secret exists and when Using older software and some boot images. Enter enable password: Cisco Enter the virtual terminal password: Telnet Configure SNMP Network Management? [yes]: no Configure IP? [yes] <Return>        Configure IGRP Routing? [yes]: no        Configure RIP Routing? [yes]: no Configure Interfaces:        Configuring interface Ethernet 0:        Is this interface in use? [yes] no        Configuring interface Ethernet 1:        Is this interface in use? [yes] no        Configuring interface Serial 0:        Is this interface in use? [yes] <Return> Configure IP on this interface? [yes] <Return> Configure IP unnumbered on this interface? [no] : <Return> IP Address for this interface: 172.29.3.4        Number of bits in subnet field [8]: <Return> Class B network is 172.29.0.0, 8 subnet bits; mask is      255.255.255.0        Configuring interface Serial 1:        Is this interface in use? [yes] <Return> Configure IP on this interface? [yes] <Return> Configure IP unnumbered on interface? [no] : <Return>        IP Address for this interface: 172.29.4.3        Number of bits in subnet field [8]: <Return> Class B network is 172.29.0.0, 8 subnet bits; mask is      255.255.255.0 

Now we have configured the two serial interfaces, set up our passwords, and chosen any routing protocols we want to utilize. For the sake of simplicity, however, we did not turn on either the Routing Information Protocol (RIP) or the Interior Gateway Routing Protocol (IGRP). The router will then show us the configuration that we created:

 The following configuration command script was created: Hostname NFLD Enable secret 5 09371034073401823 Enable password Cisco Line vty 0 4 Password Telnet No snmp-server ! ip routing ! interface Ethernet 0 Shutdown No ip address Interface Ethernet 1 Shutdown No ip address Interface Serial 0 Ip address 172.29.3.4 255.255.255.0 Interface Serial 1 Ip address 172.29.4.3 255.255.255.0 ! end Use this configuration? [yes/no]: yes 

We have now completed the initial configuration dialog and successfully configured the NFLD router with IP addressing.