Hi Andy, Verio says they accept old class-a space at the /22 orshorter level so that isn't it. I am fairly certain you can not successfully multihome with PA class-A space.. If you are not announcing that /22 to AT&T then anyone that is single-homed to AT&T (or preferring them) will probably not be able to reach your /22. I ran into this problem with some 4/8 space that Level3 assigned to me by mistake. So you are dealing with more of a Policy issue rather than general prefix filter. -Scott ----- Original Message ----- From: "Andy Ellifson" <andy@ellifson.com> To: <nanog@merit.edu> Sent: Wednesday, October 15, 2003 6:28 PM Subject: Re: Pitfalls of annoucing /24s
I have a /24 allocated to my by XO Communications in Phoenix, AZ (67.X.X.0/24). I am currently announcing it to Verio in Europe. A friend of mine that is an XO customer in Phoenix with BGP to XO can get to that address block within XO's network.
But on the flip side. I also have a /22 from AT&T (12.X.X.0/22). When I announce that network block to Verio in Europe (and nowhere else), only certain places get to the Europe location. Networks that prefer AT&T go to AT&T's network and die since the route isn't there. I don't know if I am missing something but it think it may have to do with how the network's peering/filter schemes work.
I may just be walking around the problem since I am a transit customer of Verio and they normally filter.
-Andy
--- Phil Rosenthal <pr@isprime.com> wrote:
On Oct 15, 2003, at 5:24 PM, H. Michael Smith, Jr. wrote:
What about the /24's that many ISPs (especially tier 2-3) are
assigning
to multi-homed customers? What about an IX or "critical infrastructure providers" that may be issued a /24 from ARIN (Policy 2001-3)?
As long as it's provider assigned, and your provider announces the supernet that the /24 is from, it will still work. If you announce PI space out of the old class A space in /24's, many networks wont be able to reach you.