--- On Wed, 8/29/12, Nick Olsen <[email protected]> wrote: > From: Nick Olsen <[email protected]> > Subject: Level 3 BGP Advertisements > To: [email protected] > 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
