Gmail MX over IPv6

[Mansoor Nathani]

After turning off Router Advertisements from a cisco device on the network,
I get the expected Network is unreachable message when the MTA tries IPv6
and right after that the message goes through using v4.

Thank you for your assistance.

Jun 21 03:41:48 onion postfix/qmgr[1348]: 3CCDA1A1123: from=<
root at example.com>, size=452, nrcpt=1 (queue active)
Jun 21 03:41:48 onion postfix/smtp[22635]: connect to
gmail-smtp-in-v4v6.l.google.com[2001:4860:b007::1a]:25: Network is
unreachable
Jun 21 03:41:50 onion postfix/smtp[22635]: 3CCDA1A1123: to=<
myaddress at gmail.com>, relay=gmail-smtp-in-v4v6.l.google.com[209.85.225.26]:25,
delay=1.9, delays=0.21/0.02/0.86/0.84, dsn=2.0.0, status=sent (250 2.0.0 OK
1340264510 ab7si1761286igc.10)
Jun 21 03:41:50 onion postfix/qmgr[1348]: 3CCDA1A1123: removed


On Thu, Jun 21, 2012 at 3:32 AM, Bernhard Schmidt <berni at birkenwald.de>wrote:

> Am 21.06.2012 09:28, schrieb Mansoor Nathani:
>
> Hi,
>
> > I noticed it seems to be picking up some ip / address info from an IPv6
> > tunnel to Hurricane Electric.
> >
> > I never configured this host with any such IPv6 information however.
> > The tunnel is using 2001:470:b148::/48 .
>
> Well, someone in your network obviously did.
>
> > 2001:470:b148::/48 dev eth0  proto kernel  metric 256  expires 0sec mtu
> > default via fe80::205:32ff:fee8:8b61 dev eth0  proto kernel  metric 1024
> >  expires 0sec mtu 1500 advmss 1440 hoplimit 64
>
> The device with the MAC address 00:05:32:e8:8b:61 is sending router
> advertisements with the prefix 2001:470:b148::/48 . Lucky (or unlucky)
> for you they are wrongly advertising a /48, not a /64, so SLAAC does not
> work and you don't get an address assigned. I'm a bit confused at the
> moment, since I thought Linux was handling "has defaultroute but not a
> global address" correctly these days, but obviously there are still some
> issues.
>
> Hunt down that bogus advertisement, that should solve the problem.
>
> Bernhard
>
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