--- 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) FLSPEED 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