RE: Regarding Ripv2 summarization

Raghav-

Having 4 interfaces in the same 1.1.1.0/24 network is a pretty good trick.

Are you using VRFs or did you intend to show /32 for each loopback?

If you are using /32 for those loopbacks, here is what we could expect:

I used 12.4(15)T10 for this example.

My topology is similar, using the following:

R1 Fa0/0 - Fa0/0 R3

R1 and R3 happen to be connected on the 10.234.0.0/24 subnet.

R3 with 4 32bit loopacks, advertised in RIP, ver2 with no auto-summary

On R1, using debug ip rip, while R3 is advertising the 1.1.1.x/32 networks

R1#

RIP: received v2 update from 10.234.0.3 on FastEthernet0/0

     1.1.1.1/32 via 0.0.0.0 in 1 hops

     1.1.1.2/32 via 0.0.0.0 in 1 hops

     1.1.1.3/32 via 0.0.0.0 in 1 hops

     1.1.1.4/32 via 0.0.0.0 in 1 hops

     10.33.0.0/24 via 0.0.0.0 in 1 hops

Add 1.1.0.0/16 summary on R3

R3(config-if)#ip summary-address rip 1.1.0.0 255.255.0.0

Back to R1:

RIP: received v2 update from 10.234.0.3 on FastEthernet0/0

     1.1.0.0/16 via 0.0.0.0 in 1 hops

     10.33.0.0/24 via 0.0.0.0 in 1 hops

R1#

Disabled split horizon on r3

R3(config-if)#no ip split-horizon

R1#

RIP: received v2 update from 10.234.0.3 on FastEthernet0/0

     1.1.0.0/16 via 0.0.0.0 in 1 hops

     10.33.0.0/24 via 0.0.0.0 in 1 hops

     10.234.0.0/24 via 0.0.0.0 in 1 hops

Notice, we picked up the 10.234.0.0/24 as an advertisement due to the lack
of split horizon on R3, but we still have the summary only.

Perhaps a clear ip route *, would assist if the info you are looking at in
the routing table is dated.

Best wishes,

Keith.

-----Original Message-----
From: nobody_at_groupstudy.com [mailto:nobody_at_groupstudy.com] On Behalf Of
Raghav Bhargava
Sent: Tuesday, April 20, 2010 11:48 AM
To: Cisco certification
Subject: Regarding Ripv2 summarization

Hi Experts,

My topology is as follows:

R1:se0/1 <-----> R3:se0/1

lo1: 1.1.1.1/24
lo2: 1.1.1.2/24
lo3: 1.1.1.3/24
lo4: 1.1.1.4/24

I have 4 loopbacks on R3 and i configured the summary address command on R3
to advertise the supernet to R1. Now when i check the routing table on R1
i see the aggregate address as well as the 4 prefixes in the routing table.
Now i am curious why the summarization didn't work .

I figured out one thing from this doc:- *
http://www.cisco.com/en/US/docs/ios/12_0t/12_0t7/feature/guide/sumadr.html*

that if split horizon is enabled on R3 , R1 will see everything i.e- all the
prefixes as well as the aggregate. Somehow i couldn't understand the
relation.
Although i disabled split horizon on R3 and then i only see the aggregate on
R1 but i still want to know how it worked.

Please can anyone shed some light

-- 
Warm Regards
Raghav
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