Interface Status Codes and IP Addresses

In a router, interface status codes are used to indicate the status of a physical interface. These codes can help in troubleshooting and identifying problems with the interface. Some common status codes are:

Up: the interface is operational and able to forward packets

Down: the interface is not operational

Admin down: the interface has been manually disabled

When configuring an interface on a router, an IP address must be assigned to it. The IP address is used to uniquely identify the interface on the network. IP addresses consist of a network address and a host address. The network address identifies the network to which the interface belongs, while the host address identifies the interface within the network.

Usually there are two types of physical interfaces on routers as

The Ethernet interface has the fastest speed possible on the interface.
Serial interface usually connect to PPP leased lines and Frame Relay access link. Serial interface is to be configured for different data link layer protocol like HDLC, PPP or Frame Relay but it defaults to HDLC.

Routers use two or three numbers to distinguish between different interfaces of same type and are separated by a slash like fastEthernet 0/1 and serial 1/0/1. All interfaces of router need an IP address else without an IP address even with an up-up state of interface, the router will not use the interface. IP address is configured similar to as that of switch, with an IP address and mask by using the ip address address mask interface subcommand.