How to Configure a Cisco Network

Part of the Cisco Networking All-in-One For Dummies Cheat Sheet

Like all networks, a Cisco network needs to be properly configured. To do so, you need to know the configuration modes to use when configuring your network. You also should know how to configure an interface, configure a switch management interface, and configure an interface to use DHCP for your Cisco network.

Configuration modes for Cisco networking

When moving around in the Cisco IOS, you will see many prompts. These prompts change as you move from one configuration mode to another. Here is a summary of the major configuration modes:

  • User EXEC mode: When you connect to a Cisco device the default configuration mode is user exec mode. With user exec mode you can view the settings on the device but not make any changes. You know you are in User EXEC mode because the IOS prompt displays a ">".

  • Privileged EXEC mode: In order to make changes to the device you must navigate to Privileged EXEC mode where you may be required to input a password. Privileged EXEC mode displays with a "#" in the prompt.

  • Global Configuration mode: Global Configuration mode is where you go to make global changes to the router such as the hostname. To navigate to Global Configuration mode from Privileged EXEC mode you type "configure terminal" or "conf t" where you will be placed at the "(config)#" prompt.

  • Sub Prompts: There are a number of different sub prompts from Global Configuration mode you can navigate to such as the interface prompts to modify settings on a specific interface, or the line prompts to modify the different ports on the device.

Configure an interface for Cisco networking

When working with routers in particular, but also when dealing the management interface on switches, you will often need to configure network interfaces which will either match physical interface ports or virtual interfaces in the form of a virtual LAN (VLAN) interface (when dealing with switches).

For your router interfaces the following example will set speed, duplex and IP configuration information for the interface FastEthernet 0/0 (notice the interface reference as slot/port). In the case of the router, the interface is enabled using the no shutdown command in the final step; interfaces on switches are enabled by default.

Router1>enable
Router1#configure terminal
Router1(config)#interface FastEthernet0/0
Router1(config-if)#description Private LAN
Router1(config-if)#speed 100
Router1(config-if)#duplex full
Router1(config-if)#ip address 192.168.1.1 255.255.255.0
Router1(config-if)#no shutdown

Configure a switch management interface for Cisco networking

For your switches, to enable an IP address on your management interface, you will use something similar to this example. In this example, management is being performed over VLAN 1 - the default VLAN.

Switch1>enable
Switch1#configure terminal
Switch1#interface VLAN 1
Switch1(config-if)#ip address 192.168.1.241 255.255.255.0

Configure an interface to use DHCP for Cisco networking

If you want to configure either a router or switch to retrieve its IP configuration information from a network Dynamic Host Configuration Protocol (DHCP) server, then you can commands like the following example.

Router1>enable
Router1#configure terminal
Router1(config)#interface FastEthernet0/0
Router1(config-if)#ip dhcp
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