Bind 9.2.0 and 9.2.1 stop resolving external IPs after a bit. HELP

Mark_Andrews at Mark_Andrews at
Mon Dec 2 06:38:35 UTC 2002

> My primary DNS server is up to date on the latest RH patches. It runs
> Bind 9.2.1. The backup DNS server has not been updated yet and runs
> 9.2.0. It suffers the same problem, but since it's not under load, the
> problem does not show itself until the primary DNS fails for a bit.
> As for making the root name servers mad, I did a packet capture when Bind is
> running correctly. Looking at it in ethereal, 
> I see an A query to 
>  respoinds back with "Standard Query Responce, Format
> Error" 
> The request is made again, and this time it works.
> I see a lot of "Format" errors in my packet capture and this is when Bind
> is working. 
	FORMERR's are responses to EDNS probes.  Named re-tries w/o EDNS.

	Everything sounds like normal.
> When Bind quit working last, I did a quick tcpdump and noticed that it
> was sending request out, but nothing was coming back. I did not get a
> chance to do a packet capture or a little sniffing on the external side
> of the firewall, but the backup DNS server was running fine at the time
> so I don't think it's firewall or network related. It was just like the
> root name servers stopped talking to it. Restarting Bind fixed the
> problem. Next time it goes out, I will be ready. 

	I was on a doubly NAT'd net the other day and observed the behaviour.
	As this was in a hotel conference room it wasn't worth expending
	time and effort to chase the problem down.  Note however the
	first NAT box was Linux based.

	Restarting named causes named to use a different source port which
	would allow the NAT to clear state.

	I would be taking packet traces from the outside of the firewall
	next time it fails.
> Thanks for the tip o the source rpms. When it dies again, I will try
> that. 
> Thanks
> Ed

Mark Andrews, Internet Software Consortium
1 Seymour St., Dundas Valley, NSW 2117, Australia
PHONE: +61 2 9871 4742                 INTERNET: Mark.Andrews at

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