Sunday, August 25, 2019

ISP with odd "blackhole" issue.

Hi all,

I'm a shiny new Network Engineer though have a decent amount of background in IT and Networking. Earlier this year I started work at an ISP and everything was running smoothly. I was handed an issue about a month ago where traffic seems to mysteriously vanish for (as far as I can tell) all of our IP ranges, as if our AS is being rejected somewhere.

This only happens to certain destinations, though there is no pattern between the route, dest. AS, dest. IP, or Transit used.

We managed to resolve this for one destination network by peering with them directly at LINX.

What would you guys check here? So far I've attempted reaching out to the NOCs on the destination networks and seeing if they can contact their upstreams, but that's not yielded a lot of return and I'm unsure how else I can investigate this since it's outside of our network.

Look forward to hearing from you all.

Edit: Just thought I'd add - we're not on any blacklists per my exhaustive checks. I've probably checked a good 100 or so at least. Additionally we have had issues with IP Geolocation, where we're showing up as being in the Netherlands, but I don't see how this could prevent some customers for playing games, for example. We're in the UK.



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