Unexpected behaviour from the B root servers? Am I setup wrong?
Stephen John Smoogen
smooge at gmail.com
Mon Feb 26 17:43:44 UTC 2007
On 2/25/07, Mark Andrews <Mark_Andrews at isc.org> wrote:
> > I am only seeing this with the B systems at the moment.. and I am
> > trying to figure out how I should 'fix' my firewall or backbone DNS
> > server to deal with it.
> > Our campus DNS servers will 'proxy' a request to the backbone DNS
> > servers and when it talks to the B servers, we get requests back from
> > different IP address from what we sent to (thus our firewall drops it
> > as a bad session).
> > 126.96.36.199.32768 > 188.8.131.52.domain
> > 184.108.40.206.domain > 220.127.116.11.32768
> > 18.104.22.168.domain > 22.214.171.124.32768
> > 126.96.36.199.domain > 188.8.131.52.32768
> > This really picked up on Saturday when pretty much every send to the
> > 184.108.40.206 server got 1 to 2 other returns from b1.ip4.int,
> > b2.ip4.int etc.
> > The only other servers that the firewall seems to be dropping are some
> > 'questionable' ones in Romania that showed up over the weekend.
> The first thing you need to do is figure out where the
> "duplication" is occuring.
> As a datapoint, I don't see it from here when talking to
I ran a tcpdump overnight to see when it was occuring and it seems to
occur every 10-30 queries. So my guess is that Peter Bambier's comment
about a load-balancer on the B side may be the issue. Looking at the
full packet capture the packets I am getting from 200,202,203 are all
the same as the ones I get from 201.
Hope you are having a good summer.
> 15:45:37.180796 220.127.116.11.60656 > 18.104.22.168.53: 36120 TXT CHAOS? hostname.bind. (31)
> 15:45:37.337522 22.214.171.124.53 > 126.96.36.199.60656: 36120*- 1/1/0 CHAOS TXT b2 (60) (DF)
Stephen J Smoogen. -- CSIRT/Linux System Administrator
How far that little candle throws his beams! So shines a good deed
in a naughty world. = Shakespeare. "The Merchant of Venice"
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