validating reachability via an ISP
geier at geier.ne.tz
Thu Mar 29 05:00:22 UTC 2018
On 3/29/2018 2:22 AM, Andy Litzinger wrote:
> Hi all,
> I have an enterprise network and do not provide transit. In one of our
> datacenters we have our own prefixes and rely on two ISPs as BGP neighbors
> to provide global reachability for our prefixes. One is a large regional
> provider and the other is a large global provider.
> Recently we took our link to the global provider offline to perform
> maintenance on our router. Nearly immediately we were hit with alerts that
> our prefix was unreachable and BGPMon alerted that nearly 80 AS's noted our
> route had been withdrawn. We were not unreachable from every AS, but we
> certainly were from some of the largest.
> The root cause is that the our prefix is not being adequately
> re-distributed globally by the regional ISP. This is unexpected and we are
> working through this with them now.
> My question is, how can I monitor global reachability for a prefix via this
> or any specific provider I use over time? Are there various route-servers
> I can programmatically query for my prefix and get results that include AS
> paths? Then I could verify that an "acceptable" number of paths exist that
> include the AS of the all the ISPs I rely upon. And what would an
> "acceptable" number of alternate paths be?
If your global provider supports, you could send your announcements with
a BGP community per RFC1998 telling them to not-prefer-so-much that
advertisement, "use it as a backup".
that would shift a lot of incoming traffic to the other link (regional
You'll still have the global provider link.
this is a smaller change towards taking global provider offline, keeping
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