Strange Reachability Issue

Jared Mauch jared at
Tue Sep 4 14:12:56 UTC 2012

I know a few folks from NTT have looked into this.  If someone
from KPN would get in touch with Bryn I'm sure the issue could be
quickly resolved.

- Jared

On Sep 4, 2012, at 9:18 AM, Brandt, Ralph wrote:

> I will bet that will bet that within 48 hours of you checking and
> posting this the problem will mysteriously go away. 
> Ralph Brandt
> Mechanicsburg PA 17055
> -----Original Message-----
> From: Bryn Sadler [mailto:bryn.sadler at] 
> Sent: Tuesday, September 04, 2012 9:02 AM
> To: nanog at
> Subject: Strange Reachability Issue
> 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
> This message has been scanned for viruses by essensys mailcontrol

More information about the NANOG mailing list