Configuring interfaces on a Cisco router
what is an interface?
All cables connected to the router except the power cable would be connected to an interface. This is the place where you send data in and out :)
Cisco interface naming is very simple. Individual interfaces are referred to by
media type slot#/port#
"Media type" refers to the type of media that the port is on, such as FastEthernet, serial, etc. Slot numbers are only applicable for routers that provide slots into which you can install modules (these are called modular routers). Not to worry too much, anyway these slots are numbered on the router.
Port number refers to the port within the module and numbering starts at 0.
For example, on a basic Cisco 2800 series router the 2 FastEthernet ports would be fastethernet 0/0 (module 0/ port 0)and
fastethernet 0/1 (module 0/ port 1)
both ports belong to module 0
Lets look at an example of configuring a serial port with an IP address:
Dumbledore#config term
Dumbledore(config)#interface serial 0/0
Dumbledore(config-if)#ip address 1.1.1.1 255.255.255.0
Dumbledore(config-if)#no shutdown
Dumbledore(config-if)#ctrl-Z
Dumbledore#
Then to verify configuration:
Dumbledore#show interface serial 0/0
The “no shutdown” command Brings up the interface from its shutdown state.
If ever you want to shutdown an interface
you just go into the config mode
Dumbledore#config t
Dumbledore(config)#interface serial 0/0
Dumbledore(config-if)#shutdown
Dumbledore(config-if)#ctrl-Z
and check the interface using
Dumbledore#show interface serial 0/0
In the Cisco IOS, the way to reverse or delete the results of many commands is to simply put no in front of it. For instance, to remove the IP address assigned to interface serial 0/0
Dumbledore#config t
Dumbledore(config)#interface serail 0/0
Dumbledore(config-if)#no ip address 1.1.1.1 255.255.255.0
Dumbledore(config-if)ctrl-Z
Dumbledore#show interface serial 0/0
To enable most interfaces for LAN connections, you just need to configure the IP address and issue the “no shutdown” (no shut for short) to bring the interface up.
Disclaimer
This document is to help you configure Cisco routers. We do not guarantee the accuracy of information in this document. Use at your own risk. The author will not be liable for any damages that occur as a result of using this document.