AIS AI2524 user manual 1Interior, System, and Exterior Routes, No validate-update-source

Chapter 8: AI2524 Protocol Configuration Steps

Validate Source IP Addresses

To disable the default function that validates the source IP addresses of incoming routing updates, type this command in router configura tion mode:

no validate-update-source

Network Illustration

IGRP advertises three types of routes: interior, system, and exterior, as shown in Figure 8-1. Interior routes are routes between subnets in the network attached to a router interface. If the network attached to a router is not subnetted, IGRP does not advertise interior routes.

Figure 8-1:Interior, System, and Exterior Routes

System routes are routes to networks within an autonomous system. The Cisco IOS software derives system routes from directly connected network interfaces and system route information provided by other IGRP-speaking routers or access servers. System routes do not include subnet information.

Exterior routes are routes to networks outside the autonomous system that are considered when identifying a gateway of last resort. Th Cisco IOS software chooses a gateway of last resort from the list of ex- terior routes that IGRP provides. The software uses the gateway (router) of last resort if it does not have a better route for a packet and the destination is not a connected network. If the autonomous system has more than one connection to an external network, different routers can choose different exterior routers as the gateway of last resort.

August 1997	Page 8-15
2524UM