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Re: disabling ipV6


Tony van der Hoff a écrit :
> I run my own caching BIND9 under squeeze, and as far as I'm aware it's 
> correctly set up.
> I'm using Thunderbird as my MUA, with an IMAP host on my VPS, 
> smtp.vanderhoff.org.
> When trying to read or send mail I invariably get a DNS timeout:
> Dec 28 10:11:23 tony-lx named[1768]: error (unexpected RCODE SERVFAIL) 
> resolving 'smtp.vanderhoff.org/AAAA/IN':

The authoritative DNS servers for your domain, ns0.ukpost.com and
ns1.ukpost.com, are broken. If the domain name smtp.vanderhoff.org has
no record of a given type (AAAA or other), the NS should not reply with
status=SERVFAIL but with status=NOERROR and answer=0.

> Dec 28 10:11:27 tony-lx named[1768]: error (network unreachable) 
> resolving 'smtp.vanderhoff.org/AAAA/IN': 2001:41d0:1:d640::1#53

That is perfectly normal if your caching NS server has no IPv6
connectivity. It should not cause any delay.

> Well, that appears to be looking for an IPv6 address, and as my router 
> doesn't support IPv6, it's bound to go wrong.

No. Lack of IPv6 support should be handled gracefully.

> Any suggestions, please?

1) Ask your registrar to fix their DNS servers.

2) Disable IPv6 resolution in Thunderbird by setting
network.dns.disableIPv6=true in the config editor.

3) Disable IPv6 in BIND by adding -4 in the OPTIONS line in
/etc/default/bind9. That will stop the "network unreachable" messages.
Alternatively, add the option "forward only;" so that BIND will query
only the IPv4 addresses defined in the forwarders option and will not
try to perform its own recursive resolution if they fail.

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