Why are only com/net/org slow?

[W Sanders]

This doesn't seem to have much to do with BIND, but it's one I have not
seen before. We operate some cache-only DNS servers for customers to
point their resolvers to. Most of these are running BIND 9.4.1+.

On all the hosts I've tested so far, when I do a 

dig @ourserver somedomain.com 
dig @ourserver somedomain.net
dig @ourserver somedomain.org 

it takes 4+ sec to get the initial non-cached response, whether valid
or
NXDOMAIN, back from com/net/org. In fact org often *hangs*.

All other TLDs, and ".", are fast and behave as expected.

I can reproduce this from several of our cache-only servers, in a
variety of geographic locations.

It's killing people who are (ab)using our servers to lookup up DNS
records for antispam purposes, since spammer's garbage domain names
will not be cached, and take a while to look up or even time out.

It's most likely some bizarre problem on our networks (we have a lot of
split routes etc), especially since .org hangs occasionally for valid
name lookups. I haven't the foggiest idea how to debug this
further. Anyone seen this?

Thanks - W Sanders 
http://wsanders.net


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