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Re: Level 3 BGP Advertisements
From: Randy <randy_94108 () yahoo com>
Date: Wed, 29 Aug 2012 12:49:24 -0700 (PDT)

--- On Wed, 8/29/12, Nick Olsen <nick () flhsi com> wrote:

From: Nick Olsen <nick () flhsi com>
Subject: Level 3 BGP Advertisements
To: nanog () nanog org
Date: Wednesday, August 29, 2012, 12:28 PM
Greetings all.

In practice, We've always advertised our space all the way
down to /24's 
but also the aggregate block (the /20 or the /21). Just so
there was still 
reachability to our network in the event that someone made
the foolish 
mistake of filtering lets say prefixes smaller /23...

Anyways, I've always thought that was standard practice. And
its never been 
a problem. Until we brought up peering with level 3..

I noticed that while the /24's made it out to the world. The
larger 
counterparts (2 /21's and a /20) did not. So, I start
sniffing around. Find 
that I do indeed see the prefixes in Level 3's looking glass
but they 
aren't handing it off to peers. So, Naturally, I land on
this being some 
kind of prefix filtering issue and open a ticket with Level
3. They tell me 
this is standard practice. And If I want to see the /20 or
/21's make it 
out to the rest of the world, I need to stop sending the
/24's.

Does this sound normal?
Is what I'm doing (Advertising the aggregate prefix) a good
rule of thumb?

Any other thoughts?

Nick Olsen
Network Operations (855) FLSPEEDĀ  x106

 
my 2 cents: I would think L3 would announce the /20 and /21's and no-export the /24

Why announce more-specifics if you can get away with a few shorter-prefixes.

Do you have a setup where you have to announce /24's? If you can do with a /20 and two /21's, that would be the way to 
go.
./Randy


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