January 2002
Beginner
238 pages
6h 20m
English
Content preview from IP Routing
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Default Routes
IGRP tracks
default routes in the exterior section of its routing updates. A
router receiving 10.0.0.0 in the exterior section
of a routing update would mark 10.0.0.0 as a
default route and install its next hop to 10.0.0.0
as the gateway of last resort
. Consider the network in Figure 3-6 as an example in which a core router connects
to several branch routers in remote sites.
Figure 3-6. Branch offices only need a default route
The core router is configured as follows:
hostname core1
!
interface Ethernet0
ip address 192.168.1.1 255.255.255.0
...
interface Serial0
ip address 172.16.245.1 255.255.255.0
...
router igrp 10
3 redistribute static
network 172.16.0.0
4 default-metric 10000 100 255 1 1500
!
no ip classless
5 ip default-network 10.0.0.0
6 ip route 10.0.0.0 255.0.0.0 Null0The branch router is configured as follows:
hostname branch1 ... interface Serial0 ip address 172.16.245.2 255.255.255.0 ... router igrp 10 redistribute static network 172.16.0.0 ! no ip classless
An examination of branch1’s routing table would show:
branch1#sh ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - 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 ...
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