nanog mailing list archives
Re: validating reachability via an ISP
From: Andy Litzinger <andy.litzinger.lists () gmail com>
Date: Wed, 4 Apr 2018 16:24:19 -0700
Hi Andrew, thanks for sharing your repo, it looks very relevant and I should be able to get it to do what I want with a slight tweak to the regex's. Hopefully the route-views collectors or some other ones I dig up will be able to adequately show at least 3 AS path hops through my regional provider to get to my AS/prefix. I really want to see AS paths where there are at least 2 different AS hops before my regional providers AS. This will help me feel good that the global partners of my regional ISP are re-advertising my prefix to their peers. Otherwise if the AS path only includes the first and second hop upstream I can only infer that the 2nd hop AS is accepting routes from the 1st hop AS (my regional ISP), but not that the 2nd hop AS is actually re-advertising the route to anyone else. thanks! -andy On Thu, Mar 29, 2018 at 7:51 AM, Andrew Wentzell <awentzell () gmail com> wrote:
On Wed, Mar 28, 2018 at 7:22 PM, Andy Litzinger <andy.litzinger.lists () gmail com> 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 BGPneighborsto 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we were hit with alertsthatour prefix was unreachable and BGPMon alerted that nearly 80 AS's notedourroute had been withdrawn.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 weareworking through this with them now. My question is, how can I monitor global reachability for a prefix viathisor any specific provider I use over time? Are there variousroute-serversI can programmatically query for my prefix and get results that includeASpaths? Then I could verify that an "acceptable" number of paths existthatinclude the AS of the all the ISPs I rely upon. And what would an "acceptable" number of alternate paths be?I did something similar a few years ago, by querying routeviews and validating AS paths using python and pexpect. You could adapt it for your use pretty easily. The code's here: https://github.com/awentzell/check-as-path
Current thread:
- Re: validating reachability via an ISP Don Thomas Jacob (Apr 04)
- <Possible follow-ups>
- Re: validating reachability via an ISP Andy Litzinger (Apr 04)
- Re: validating reachability via an ISP Andy Litzinger (Apr 04)
- Re: validating reachability via an ISP Andy Davidson (Apr 05)
- Re: validating reachability via an ISP Ben Bartsch (Apr 05)
- Re: validating reachability via an ISP Andy Litzinger (Apr 05)