Strange Reachability Issue

Bryn Sadler bryn.sadler at
Tue Sep 4 13:01:51 UTC 2012

Hello all,

I was wondering if anyone might be able to share their thoughts on a strange issue we're experiencing with NTT at the moment. We're AS48273 and are advertising a prefix through AS 8190 (single upstream provider at the moment). We've been doing this for some years now, and all has been fine. The last few days we seem to have disappeared from NTT's worldwide routing tables, with the exception of Europe. If we use their looking glass to query any NTT european router we can see the prefix, being learned via AS 286 then AS 8190, as expected. If we look at any other router outside of europe, there is simply no entry for that prefix. Elsewhere in the world we seem to be fine, we're in every other network I've looked at and general reachability is fine.

First step was to contact the NTT NOC, and they've confirmed that there's no Internal routing/config issue on their network, but that they cannot discuss their peering arrangements due to NDAs. We've also picked it up with KPN (AS 286), who have verified that the prefix is visible throughout their network (true), and that they are advertising it to NTT. One thing of note is that Global Crossing are learning our prefix from KPN as well, and the prefix is showing fine in their global tables.

We seem to be caught in the classic finger pointing scenario, but I can't get my head around why the prefix is visible in NTT Europe, but not anywhere else, unless they have a config error somewhere on their network. We've checked a few of the routes from AS 8190 and they are in the NTT global tables just fine, and at least in Europe they seem to have the same community values etc. We're still following on with NTT, but can anyone offer some wisdom for new avenues to pursue?

Thanks for your help,

Bryn Sadler

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