Confused by routing table entry

ccna-student

Hi, First off I'm sorry if this is a really stupid question.

Basically I've been following the CBT NUggets for ICND1 and have recreated the LAB topology Jeremy Cioara uses.

I'm currently implementing dynamic routing using RIP. When I view the routing table on my routers

Gateway of last resort is not set

68.0.0.0/8 is variably subnetted, 2 subnets, 2 masks
R 68.0.0.0/8 [120/2] via 192.168.2.1, 00:00:24, Serial0/0
R 68.110.171.96/27 [120/2] via 192.168.2.1, 00:00:25, Serial0/0
R 192.168.1.0/24 [120/1] via 192.168.2.1, 00:00:24, Serial0/0
C 192.168.2.0/24 is directly connected, Serial0/0
C 192.168.3.0/24 is directly connected, FastEthernet0/0

and

68.0.0.0/27 is subnetted, 1 subnets
C 68.110.171.96 is directly connected, FastEthernet0/0
C 192.168.1.0/24 is directly connected, FastEthernet0/1

I see the entries 68.0.0.0/8 is variably subnetted, 2 subnets, 2 masks & 68.0.0.0/27 is subnetted, 1 subnets.

What is confusing me is that one router is showing 68.0.0.0 with it's class A mask and the other uses the /27 mask. I tried builing the LAB using 10.1.1.0/24 addresses and it was even more confussing.

Can anyone explain this to me as I am stuck? Thanks.

dtlokee

If you are using RIP v1 then it will summarize at classful boundries, RIP v2 will also do this by default but can be turned of with the "no auto-summary" command. Looking at the routing tables it looks like you have the routers connected FA0/0 - Fa0/0 which is using the classful 192.168.1.0/24 and the routers at both ends have a 68.x.x.x. The routers will advertise the summary 68.0.0.0/8 between them. Now because that route is only showing up on one router it may indicate you have "auto-summary" on one and "no auto-summary" on the other running RIP v2.