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
Blogs and organic groups at http://www.ccie.net