[BlueOnyx:11406] Re: 5108R IPv6 fun fact [dovecot issue solved]

[Gerald Waugh]

On 09/24/2012 10:34 PM, Chris Gebhardt - VIRTBIZ Internet wrote:
> Michael Stauber wrote:
>> Hi all,
>>
>> Ok, this is indeed something funny and needs to be looked at.
>>
>> I tried to make sense about the suggestions as to what needs fixed where
>> to disable IPv6 entirely.
> If it may please the court, may I submit we have IPv6 disabled by
> default, but not completely removed... just in case we might like to
> make some manual entries so that we could use IPv6 if desired?
>
> We're actually doing this "on purpose" on a couple of boxes, and I have
> another couple of customers who are also experimenting.
>
>> Can someone please summarize this again for me in one message? Thanks!
> Sure thing.  One of my hosting boxes "magically" grabbed an IPv6 address
> using auto discover.  Sendmail attached to the IPv6 IP.  Our nameservers
> are all IPv6-enabled.  This hosting box happened to look up the
> mailserver for comcast.net:
>
> mx1.comcast.net.        300     IN      A       68.87.26.147
> mx1.comcast.net.        48      IN      AAAA    2001:558:fe14:70::22
> mx2.comcast.net.        300     IN      A       76.96.40.147
> mx2.comcast.net.        7200    IN      AAAA    2001:558:fe2d:70::22
> dns101.comcast.net.     292     IN      A       68.87.29.164
> dns101.comcast.net.     292     IN      AAAA    2001:558:1002:a:68:87:29:164
> dns102.comcast.net.     3560    IN      A       68.87.85.132
> dns102.comcast.net.     3560    IN      AAAA    2001:558:1004:7:68:87:85:132
> dns103.comcast.net.     3560    IN      A       68.87.76.228
> dns103.comcast.net.     3560    IN      AAAA    2001:558:1014:c:68:87:76:228
> dns104.comcast.net.     3560    IN      A       68.87.68.244
> dns104.comcast.net.     3560    IN      AAAA    2001:558:100a:5:68:87:68:244
> dns105.comcast.net.     3560    IN      A       68.87.72.244
> dns105.comcast.net.     3560    IN      AAAA    2001:558:100e:5:68:87:72:244
>
>
> The box used one of the IPv6 records to connect to comcast.net.   The
> only problem here was that we did not have a proper PTR on the IPv6
> address.  We rectified that in all of about 2 minutes after noticing the
> issue, and mail went through just fine.
>
> So I suppose the issue is that for most production cases, it would be
> best to have IPv6 disabled.
>
> We happen to be making an aggressive IPv6 push, so I'm not going to be
> one of the folks who says just eliminate all IPv6.  But I do agree that
> in most cases it would be best if left disabled by default.
>
> This should be as simple as adding this to ifcfg-eth0:
> IPV6_AUTOCONF=no
>
Also we found dovecot with and ipV6 issue

fix was adding
listen = *
default is listen = ::, *
/etc/dovecot/conf.d/10-master.conf

without this fix dovecot would not start, errors, (all 3 different 
protocols)

listen(::, 110) failed: Address family not supported by protocol


-- 
Gerald

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