Cisco Systems 1900 Series manual Gateway of Last Resort, Routerconfig# ip routing

Chapter 5 Configuring the Router

Performing the Initial Configuration on the Router

Gateway of Last Resort

When default information is being passed along through a dynamic routing protocol, no further configuration is required. The system periodically scans its routing table to choose the optimal default network as its default route. In the case of RIP, there is only one choice, network 0.0.0.0. In the case of IGRP, there might be several networks that can be candidates for the system default. The Cisco IOS software uses both administrative distance and metric information to determine the default route (gateway of last resort). The selected default route appears in the gateway of last resort display of the show ip route EXEC command.

If dynamic default information is not being passed to the software, candidates for the default route are specified with the ip default-networkglobal configuration command. In this usage, the ip default-networkcommand takes an unconnected network as an argument. If this network appears in the routing table from any source (dynamic or static), it is flagged as a candidate default route and is a possible choice as the default route.

If the router has no interface on the default network, but does have a route to it, it considers this network as a candidate default path. The route candidates are examined and the best one is chosen, based on administrative distance and metric. The gateway to the best default path becomes the gateway of last resort.

SUMMARY STEPS

1.enable

2.configure terminal

3.ip routing

4.ip route dest-prefix mask next-hop-ip-address [admin-distance] [permanent]

5.ip default-network network-numberor

ip route dest-prefix mask next-hop-ip-address

6.end

7.show ip route

DETAILED STEPS

	Command or Action	Purpose
Step 1
	enable	Enables privileged EXEC mode.
		• Enter your password if prompted.
	Example:
	Router> enable
Step 2
	configure terminal	Enters global configuration mode.
	Example:
	Router# configure terminal
Step 3
	ip routing	Enables IP routing.
	Example:
	Router(config)# ip routing
		Cisco 1900 Series Hardware Installation
OL-19084-02			5-15