Level 3 BGP Advertisements

Hale, William C William.C.Hale at windstream.com
Wed Aug 29 19:52:10 UTC 2012

No, that's not standard practice.  I do this exact thing with Level 3 and have been for many many many years.  Whoever is telling you this must be green.

I would recommend adding the no-export community to your more specific routes if you can so as to be a good steward of the ever growing Internet IPv4 table.
From: Nick Olsen [nick at flhsi.com]
Sent: Wednesday, August 29, 2012 2:28 PM
To: nanog at nanog.org
Subject: Level 3 BGP Advertisements

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

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