[SLUG] ADSL/DNS/IPTables issue

[Tony Green <tgreen@xxxxxxxxxxx>]

Happy Friday Afternoon one and all,

I've got a annoyance of a problem which, I thought, was limited to my 
home ADSL connection, but I was wrong.

I upgraded my firewall at home to Debian Sarge (running 2.6 kernel) and 
quickly found some problems which didn't used to exist.  I thought it 
was MSS clamping (which I had missed), but enabling that didn't fix 
everything.

The issue is that when a desktop requests a DNS lookup, it times out 
before it comes back (5 seconds approx).  You can immediately request 
the address again and everything works fine - a simple but annoying 
work around.

I thought it was some weird setup thing with my ADSL (iiNet).  I 
switched from PPPoE on the firewall to running that on the ADSL modem - 
still no good.  I looked into MTU's, but nothing worked (went down to 
1452).

The firewall config is the same on the old and the new setups, port 53 
tcp/udp is allowed through.  I'm running bind9 on the firewall and the 
iptables is run through shorewall.

Head scratching and googling hasn't yielded much more info and now I've 
replicated the problem on a brand new, but completely separate, machine 
(same packages but on Telstra ADSL).

Concussion from a cluestick to the head is more than welcome.

Greeno
--
Tony Green <tgreen@xxxxxxxxxxx>