286
Chapter 5
IP Routing
The following router output shows the routing tables for the 2501B and
2501C routers.
2501B#sh ip route
[output cut]
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 5 subnets
R 172.16.50.0 [120/1] via 172.16.40.2, 00:00:26, Serial1
C 172.16.40.0 is directly connected, Serial1
C 172.16.30.0 is directly connected, Ethernet0
C 172.16.20.0 is directly connected, Serial0
R 172.16.10.0 [120/1] via 172.16.20.1, 00:00:04, Serial0
2501B#
RouterC#sh ip route
[output cut]
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 5 subnets
C 172.16.50.0 is directly connected, Ethernet0
C 172.16.40.0 is directly connected, Serial0
R 172.16.30.0 [120/1] via 172.16.40.1, 00:00:06, Serial0
R 172.16.20.0 [120/1] via 172.16.40.1, 00:00:06, Serial0
R 172.16.10.0 [120/2] via 172.16.40.1, 00:00:06, Serial0
RouterC#
RIP has worked well in our little internetwork. However, since this tech-
nique has a maximum hop count of only 15 hops (where 16 is deemed
unreachable) and performs full routing-table updates every 30 seconds, it
can cause havoc on a larger internetwork.
One more thing I want to show you about RIP routing tables and the
parameters used to advertise remote networks. Notice that the following
routing table shows [120/15] in the 172.16.10.0 network metric. This
means that the administrative distance is 120, the default for RIP, but that
the hop count is 15. Remember that each time a router receives an update
from another router, it increments the hop count by one for each route.
RouterC#sh ip route
[output cut]
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 5 subnets
Copyright ©2002 SYBEX, Inc., Alameda, CA
www.sybex.com