While working on my RIPv2 Supernet Support Issue which I recently discussed under RIP section of this blog, I dropped any email to Brian McGahan CCIE#8593 (http://www.internetworkexpert.com/) asking him his suggestions on my issue and the solution I discovered to fix it. Below is his reply on that issue:
From: email@example.com [mailto:firstname.lastname@example.org] On Behalf Of Brian McGahan
Sent: Sunday, January 27, 2009 9:00 AM
Subject: Re: [CCIE R&S] RIPv2 Doesn't support CIDR or supernet?
I'm not sure if this was mentioned in the thread before, since I can only see the latest post via email, but the only way to circumvent this with rip is to re-originate a new prefix for the shorter match.
For example if you want to advertise 10.0.0.0/7 into ripv2, you can't do a summary address, but you could do a static null route for the prefix and then redistibute static.
Brian McGahan, CCIE #8593 (R&S/SP/Security)
Internetwork Expert, Inc.
On Jan 24, 2009, at 5:19 PM, DarrellEscola
The "ip summary-address rip" interface command supports summarization only up to the class-ful network boundaries.
If you had 10.1.2.0/24 you could summarize this to any summary from /8 to /23, but a /7 summary would not work.
EIGRP does permit supernet summaries, including 0.0.0.0 0.0.0.0 to provide a default route for the neighbor on the interface the summary is configured on.