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we were hit with alerts that our prefix was unreachable and BGPMon alerted that nearly 80 AS's noted our route had been withdrawn.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 provider). You'll still have the global provider link. this is a smaller change towards taking global provider offline, keeping some fallback. Frank

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 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we were hit with alerts that our prefix was unreachable and BGPMon alerted that nearly 80 AS's noted our route had been withdrawn.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?

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

Hi Andy, You can use Qrator.Radar API: https://api.radar.qrator.net/. The get-all-paths method will return the set of active paths for selected prefix. 2018-03-29 2:22 GMT+03:00 Andy Litzinger <andy.litzinger.lists@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

-- | Alexander Azimov | HLL l QRATOR | tel.: +7 499 241 81 92 | mob.: +7 915 360 08 86 | skype: mitradir | mailto: aa@qrator.net | visit: www.qrator.net

On 29/03/2018, 00:22, Andy Litzinger <andy.litzinger.lists@gmail.com> wrote:

...

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.

Hi, Andy — Are you failing to advertise it, or are they filtering it on ingress, or are they failing to send it to their other peers? One configuration mishap which is starting to come along more and more partial or poor reachability caused by route objects which are not correctly published in the IRRDB. It is going to be essential to make sure that you have properly recorded IRR route objects in, for instance, RADB. More BGP speakers properly filter their peers using information that is published there. Avoid future reachability problems by checking this today! Yours, A friendly route-server operator with strict filtering -a -- Andy Davidson Asteroid International BV https://www.asteroidhq.com @asteroidhq @andyd -------------------------------------------------- Local interconnection. Where you need it.