Originating a Default Route with IGRP

As with RIP, you can configure a default route on an IGRP router like this:

router igrp network

The default route is used locally by the router; however, it cannot be advertised to any other router with IGRP. IGRP does not propagate even if you redistribute it into IGRP with the redistribute static command.

To make IGRP originate a default route and advertise it to others, configure IGRP as follows (this also works for EIGRP):

router igrp ICC redistribute static network

ip route ip default-network

where ip route creates a static route to a fictitious network (a major net). This network does not actually exist in the organization. It's just a placeholder and a substitute for ip route

The command ip default-network declares that, the fictitious network, is to be treated as a gateway of last resort. Traffic with an unknown destination is sent to this network. Ilie router knows the route to this network is through 192.168.202,1 because of the previous command, ip mute

The command redistribute static is necessary to redistribute the static route,, into IGRP so that it can be advertised to other IGRP routers. Upon receiving other routers will use it as a default route. This is equivalent to a RIP router receiving

To verity the configuration of the originator of the default, issue show ip route: IGRP-Router#sh ip ro

Codes: C • connected, S static, I • IGRP, R RIP, M - mobile, B BGP D • EIGRP, EX - EIGRP external, 0 OSPF, IA - OSPF inter area N1 OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E EGP i • IS IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * candidate default U per-user static route, o - 0DR T • traffic engineered route

Gateway of last resort is tQ network 3«.0.0.0 is subnetted, 2 subnets C is directly connected, Serial0

C is directly connected, Seriall

<lines deleted for brevity>

The preceding output agrees with the configuration: Gateway of last resort is correct, and network is codcd with S*, indicating it is a default route. If you forget to configure the ip default-network command, the asterisk (*) will not appear and the static will not be a default route.

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