RIPv1 Doesnt support route summarization.

[FaadiKhan]

Limitations of RIPv1 is that it doesn't support router summarization. The below example explains the same, but coudn't under that how route are summarized. Please help on route summarization considering the below example as a limited of RIPv1.

[Georg Pauwen]

Hello,

RIPv1 actually DOES summarize, but only to classful boundaries. Have a look at the RIP database below (v1):

R1#sh ip rip database
10.0.0.0/8 auto-summary
10.1.0.0/16 directly connected, GigabitEthernet0/1
192.168.111.0/24 auto-summary
192.168.111.0/24
[1] via 192.168.123.2, 00:00:01, GigabitEthernet0/0
192.168.123.0/24 auto-summary
192.168.123.0/24 directly connected, GigabitEthernet0/0

The problem you have in your network with RIPv1 is that the two 10 networks, 10.1.0.0/16 and 10.2.0.0/16, will not be able to reach each other, because RIPv1 does not support VLSM (Variable Length Subnet Masking), and will only send out the classful 10.0.0.0/8 network. Since that is directly connected on both ends, nothing will be sent at all.

See how the RIP database changes when you enable RIPv2:

R1#sh ip rip database
10.0.0.0/8 auto-summary
10.0.0.0/8
[2] via 192.168.123.2, 00:00:15, GigabitEthernet0/0
10.1.0.0/16 directly connected, GigabitEthernet0/1
10.2.0.0/16
[2] via 192.168.123.2, 00:00:06, GigabitEthernet0/0
192.168.111.0/24 auto-summary
192.168.111.0/24
[1] via 192.168.123.2, 00:00:15, GigabitEthernet0/0
192.168.123.0/24 auto-summary
192.168.123.0/24 directly connected, GigabitEthernet0/0

Now the VLSM mask is being sent, and both 10 networks can reach each other.

Does that make sense ?