nanog mailing list archives
Re: route for linx.net in Level3?
From: Brian Dickson <brian.peter.dickson () gmail com>
Date: Thu, 4 Apr 2013 15:53:39 -0400
Leo Bicknell wrote: Even if the exchange does not advertise the exchange LAN, it's probably the case that it is in the IGP (or at least IBGP) of everyone connected to it, and by extension all of their customers with a default route pointed at them. Actually, that may not be the case, and probably *should* not be the case. Here's why, in a nutshell: If two regional ISPs on either side of the planet, point default to the same Global ISP, even if they do not peer with that ISP, by using the IX next-hop at IX A (for ISP A), and IX B (for ISP B), then the Global ISP is now giving free on-net transit to A and B. So, it turns out that pretty much the only way to prevent this at a routing level, is to not carry IXP networks (in IGP or IBGP), but rather to do next-hop-self. The other way is to filter at a packet level on ingress, based on Layer 2 information, which on many kinds of IX-capable hardware, is actually impossible. So, when it comes to IXPs: Next-Hop-Self. (BCP 38 actually doesn't even enter into it, oddly enough.) Brian
Current thread:
- route for linx.net in Level3? John Kemp (Apr 03)
- Re: route for linx.net in Level3? Job Snijders (Apr 03)
- Re: route for linx.net in Level3? Yang Yu (Apr 03)
- Re: route for linx.net in Level3? Jay Ashworth (Apr 04)
- Re: route for linx.net in Level3? Leo Bicknell (Apr 04)
- Re: route for linx.net in Level3? Tom Paseka (Apr 04)
- RE: route for linx.net in Level3? Adam Vitkovsky (Apr 04)
- Re: route for linx.net in Level3? Paul Ferguson (Apr 04)
- Re: route for linx.net in Level3? Jay Ashworth (Apr 04)
- Re: route for linx.net in Level3? John Kemp (Apr 04)
- <Possible follow-ups>
- Re: route for linx.net in Level3? Brian Dickson (Apr 04)
- Re: route for linx.net in Level3? Joe Abley (Apr 04)
- Re: route for linx.net in Level3? Randy Bush (Apr 04)
- Re: route for linx.net in Level3? Tom Paseka (Apr 04)
- Re: route for linx.net in Level3? Randy Bush (Apr 04)
- Re: route for linx.net in Level3? Leo Bicknell (Apr 04)
- RE: route for linx.net in Level3? Adam Vitkovsky (Apr 05)
- Re: route for linx.net in Level3? Leo Bicknell (Apr 05)
- Re: route for linx.net in Level3? Joe Abley (Apr 04)