Strange Reachability Issue

Bryn Sadler bryn.sadler at
Tue Sep 4 14:20:11 UTC 2012

Many thanks to Jared for jumping on this so quickly off-list, it's much
appreciated and hopefully we're getting towards a solution now.

On 04/09/2012 15:12, "Jared Mauch" <jared at> wrote:

>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
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