My more specifics are advertise to customers only (not supposed to be visible to peers), which was how I found that TWT had transitioned from Level3 peer to customer...and I'm only going 1 bit more specific (not down to the /24s) for TE purposes. On Wed, 29 Aug 2012, Nick Olsen wrote:
Thanks for the input Jon. I should note that is exactly what we are doing. The /24's are actually tagged with the advertise to customers, prepend to peers community.
Nick Olsen Network Operations (855) FLSPEED x106
---------------------------------------- From: "Jon Lewis" <jlewis@lewis.org> Sent: Wednesday, August 29, 2012 3:48 PM To: "Nick Olsen" <nick@flhsi.com> Subject: Re: Level 3 BGP Advertisements
On Wed, 29 Aug 2012, Nick Olsen wrote:
Anyways, I've always thought that was standard practice. And its never been a problem. Until we brought up peering with level 3..
No...I'd call that global table pollution. In general, there's no reason you should announce your CIDRs and all their /24 subnets.
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?
No. I announce to Level3 our IP space and 2 subnets of each CIDR (i.e. /17 + 2 /18 subnets of that /17, etc.), but I use community tags (and other tricks) to mark the more specifics as advertise to [certain] L3 customers only, and let the less specifics out to the world. The only problems I've had with this have been when L3 peers have become customers,
and one L3 customer doing something odd (never did find out what) that caused them to effectively null route our space until I kept them from seeing the more specifics (creative abuse of loop detection).
Level3's prefix filter for your session should be built based on IRR data.
If it's not doing what you want, you probably haven't setup the IRR data properly.
---------------------------------------------------------------------- Jon Lewis, MCP :) | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________
---------------------------------------------------------------------- Jon Lewis, MCP :) | I route Senior Network Engineer | therefore you are Atlantic Net | _________ http://www.lewis.org/~jlewis/pgp for PGP public key_________