January 2002
Beginner
238 pages
6h 20m
English
Content preview from IP Routing
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Default Routes
EIGRP tracks default routes in the external section of its routing updates. Candidate default routes are marked by setting the flags field to 0x02.
Default routes are most often used to support branch offices that have only one or two connections to the core network (see Figure 4-11).
Figure 4-11. 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 eigrp 10
24 redistribute static metric 56 100 255 1 255
network 172.16.0.0
!
ip classless
25 ip route 0.0.0.0 0.0.0.0 Null0 The branch router is configured as follows:
hostname branch1
...
interface Serial0
ip address 172.16.245.2 255.255.255.0
...
26 router eigrp 10
network 172.16.0.0An examination of branch1’s routing table would show:
branch1#sh ip route
...
Gateway of last resort is 172.16.251.1 to network 0.0.0.0
172.16.0.0/24 is subnetted, 6 subnets
C 172.16.245.0 is directly connected, Serial0
...
27 D*EX 0.0.0.0/0 [170/46251776] via 172.16.245.1, 00:01:47, Serial0Since the default route is an external route, it is tagged with a distance of 170 (line 27).
The following steps were followed in the creation of this default route:
Network
0.0.0.0was defined as a static route on core1 (see line 25).Network
0.0.0.0was redistributed into EIGRP 10 (see ...
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