North American Network Operators Group

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RE: /24 multihoming issue

  • From: Ejay Hire
  • Date: Thu Oct 20 13:35:30 2005


How long did you wait to see your block come back during
testing?  I've seen it take > 60 seconds in some cases.

For redundancy with non PI IP space, It's generally only
important that the ISP you are getting the IP block from can
see both routes, and that it sees it at the same level of
localpref.  (as path differences are okay, as long as they
are consistent.)  Since the isp providing the ip space will
announce an aggregate larger than your block, you should be
reachable as long as they can see both routes to you.


> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> Behalf Of Kyaw Khine
> Sent: Wednesday, October 19, 2005 11:39 PM
> To: [email protected]
> Subject: /24 multihoming issue
> I'm having trouble announcing a single /24 from an
> ASN. ASN is multi-homed to ISP-A and ISP-B, prepending
> on ISP-B side.
> ASN in question has one and only one /24 which
> originally was from ISP-B /17 block.
> Some ISP only sees path from ISP-A and some from ISP-B
> and very few sees both paths. Apparently, when we are
> testing failover, it failed. (can't get to most of the
> internet, can't VPN in from outside, can't send mails
> etc.... BGP paht/route disappear from some of looking
> glasses)
> After the test, I registered /24 and ASN with RADB and
> things get slightly better, meaning a few more ISP
> sees both but majority of them still seeing single ISP
> path.
> I've contacted both ISPs and they both claimed they
> are announcing our /24 to the rest of the world,
> without manipulation.
> What am I missing here?
> Thanks,
> - Kyaw
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