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validating reachability via an ISP

If your prefix is larger than /24 you can test with a more specific prefix
such as a /24. Announce the test prefix on just one transit provider. Then
check with BGP services such as the looking glass service provided by the
NLNOG RING network.

There will be no interruption in the traffic as it will follow the less
specific prefix everywhere the test prefix was not picked up.

If you only have a /24 you will need to test in a service window.



Den tor. 29. mar. 2018 01.24 skrev Andy Litzinger <
andy.litzinger.lists at gmail.com>:

> 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 route had been withdrawn.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?
> thanks in advance,
>   -andy