Route Information

Route Information
Just like with other routing protocols, you should always verify that the correct information is
in the routing table:
plano#show 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, ia - IS-IS inter area
* - candidate default, U - per-user static route, o - ODR
P - periodic downloaded static route
Gateway of last resort is not set
O IA 192.168.24.0/24 [110/112] via 10.10.10.1, 00:00:02, Serial2/0.1
20.0.0.0/24 is subnetted, 1 subnets
C 20.20.20.0 is directly connected, FastEthernet2/0
172.16.0.0/24 is subnetted, 1 subnets
O IA 172.16.20.0 [110/113] via 10.10.10.1, 00:00:02, Serial2/0.1
172.20.0.0/24 is subnetted, 2 subnets
C 172.20.128.0 is directly connected, Loopback0
C 172.20.192.0 is directly connected, Loopback1
10.0.0.0/24 is subnetted, 1 subnets
C 10.10.10.0 is directly connected, Serial2/0.1
As can be seen from this routing table, there are two routes that were learned through OSPF.
You will know the routes learned from OSPF by the code O in front of the route line. The code
IA after the O means the routes are inter-area routes. If you would like to view only routes
learned by OSPF, the following command may be used:
plano#show ip route ospf
O IA 192.168.24.0/24 [110/112] via 10.10.10.1, 00:01:07, Serial2/0.1
172.16.0.0/24 is subnetted, 1 subnets
O IA 172.16.20.0 [110/113] via 10.10.10.1, 00:01:07, Serial2/0.1
Verifying and Troubleshooting OSPF 197
To view detailed information about a particular route, the following command, with the
appropriate destination attached, needs to be entered in privileged EXEC mode:
plano#show ip route 192.168.24.0
Routing entry for 192.168.24.0/24
Known via "ospf 1", distance 110, metric 112, type inter area
Last update from 10.10.10.1 on Serial2/0.1, 00:01:36 ago
Routing Descriptor Blocks:
* 10.10.10.1, from 192.168.24.1, 00:01:36 ago, via Serial2/0.1
Route metric is 112, traffic share count is 1
By viewing the detailed route information in the preceding example, you can discern that the
route was learned from OSPF process 1, the distance is 110, the metric is 112, and the route is
an inter-area route.
To view the OSPF routing information known by an ABR or ASBR, you can enter the show
ip ospf border-routers command to view the internal routing table. The following is a sample
output from this command:
plano#show ip ospf border-routers
OSPF Process 1 internal Routing Table
Codes: i - Intra-area route, I - Inter-area route
i 192.168.24.1 [48] via 10.10.10.1, Serial2/0.1, ABR, Area 0, SPF 6