Information Technology Reference
In-Depth Information
The topology table shows the L1 and L2 metrics to Router 10. The L1 metric is 40, as
configured on the IS. The L2 metric is the default value of 10.
The IS-IS database shows that Router 9 and Router 10 are L1/L2 ISs.
The Router 10 IP routing table is displayed in Example 8-27.
Example 8-27
Router 10 IP Routing Table
Router10#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 192.16.100.241 to network 0.0.0.0
i L1 10.0.0.0/8 [115/164] via 192.16.100.241, Serial0
192.16.100.0/24 is variably subnetted, 6 subnets, 3 masks
C 192.16.100.240/30 is directly connected, Serial0
C 192.16.100.32/28 is directly connected, Ethernet0
i L2 192.16.100.16/28 [115/20] via 192.16.100.241, Serial0
i L2 192.16.100.1/32 [115/25] via 192.16.100.241, Serial0
i L2 192.16.100.2/32 [115/15] via 192.16.100.241, Serial0
C 192.16.100.3/32 is directly connected, Loopback0
i*L2 0.0.0.0/0 [115/10] via 192.16.100.241, Serial0
The entry for the redistributed route 10.0.0.0 is redistributed as both L1 and L2. Router 8
displayed the route as an L2 route. Here, it is an L1 route even though Router 9 advertises both
L1 routes and L2 routes. If multiple paths exist to the same destination, as with 10.0.0.0 (path
1 is L1, path 2 is L2), the L1 path is preferred over the L2 path.
IS-IS Summary
The characteristics of IS-IS are summarized as follows:
•
Link-state protocol
•
Uses OSI PDUs between ISs
•
Classless Protocol (supports VLSMs)
•
Default metric is set to 10 for all interfaces
•
Arbitrary metric: single link max = 64, path max = 1024
Search WWH ::
Custom Search