<div>Here is the output:</div><div><br></div><div>I noticed it seems to be picking up some ip / address info from an IPv6 tunnel to Hurricane Electric.</div><div><br></div><div>I never configured this host with any such IPv6 information however.</div>
<div><br></div><div>The tunnel is using 2001:470:b148::/48 .</div><div><br></div><div>Here is an attempt to traceroute to google:</div><div><br></div><div><div>[root@onion ~]# traceroute6 <a href="http://google.com">google.com</a></div>
<div>traceroute to <a href="http://google.com">google.com</a> (2001:4860:4008:802::1001), 30 hops max, 80 byte packets</div><div> 1 fe80::205:32ff:fee8:8b61%eth0 (fe80::205:32ff:fee8:8b61%eth0) 1.729 ms 5.032 ms 5.331 ms</div>
<div> 2 * * *</div><div> 3 * * *</div></div><div><br></div><div><br></div><div>[root@onion ~]# ip -6 add</div><div>1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436</div><div> inet6 ::1/128 scope host</div><div> valid_lft forever preferred_lft forever</div>
<div>2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000</div><div> inet6 fe80::215:5dff:fe02:830a/64 scope link</div><div> valid_lft forever preferred_lft forever</div><div><br></div><div><br></div>
<div>[root@onion ~]# ip -6 route</div><div>unreachable ::/96 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div><div>unreachable ::ffff:<a href="http://0.0.0.0/96">0.0.0.0/96</a> dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div>
<div>2001:470:b148::/48 dev eth0 proto kernel metric 256 expires 0sec mtu 1500 advmss 1440 hoplimit 4294967295</div><div>unreachable 2002:a00::/24 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div>
<div>unreachable 2002:7f00::/24 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div><div>unreachable 2002:a9fe::/32 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div>
<div>unreachable 2002:ac10::/28 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div><div>unreachable 2002:c0a8::/32 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div>
<div>unreachable 2002:e000::/19 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div><div>unreachable 3ffe:ffff::/32 dev lo metric 1024 error -101 mtu 16436 advmss 16376 hoplimit 4294967295</div>
<div>fe80::/64 dev eth0 proto kernel metric 256 mtu 1500 advmss 1440 hoplimit 4294967295</div><div>default via fe80::205:32ff:fee8:8b61 dev eth0 proto kernel metric 1024 expires 0sec mtu 1500 advmss 1440 hoplimit 64</div>
<div><br></div><br><div class="gmail_quote">On Thu, Jun 21, 2012 at 3:16 AM, Gert Doering <span dir="ltr"><<a href="mailto:gert@space.net" target="_blank">gert@space.net</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
Hi,<br>
<div class="im"><br>
On Thu, Jun 21, 2012 at 02:28:31AM -0400, Mansoor Nathani wrote:<br>
> Since Gmail has enabled AAAA records for some of its MX hosts, my IPv4 only<br>
> machine gets the Gmail IPv6 address and attempts to deliver email. Its only<br>
> when the timeout has been reached will it try the IPv4 address.<br>
><br>
> I am curious if anyone else is experiencing this or perhaps I need to do<br>
> something on the CentOS 6 box to disable IPv6 till the time when it has<br>
> native IPv6 capability.<br>
><br>
> Jun 21 02:14:47 onion postfix/cleanup[1494]: 435AD1A110A:<br>
> message-id=<20120621061447.435AD1A110A@host.domain><br>
> Jun 21 02:14:47 onion postfix/qmgr[1348]: 435AD1A110A:<br>
> from=<user@host.domain>, size=448, nrcpt=1 (queue active)<br>
> Jun 21 02:15:09 onion postfix/smtp[1497]: connect to<br>
> <a href="http://gmail-smtp-in-v4v6.l.google.com" target="_blank">gmail-smtp-in-v4v6.l.google.com</a>[2001:4860:b007::1b]:25: Connection timed out<br>
<br>
</div>The more interesting question, actually, is why it actually has to wait<br>
for IPv6 to time-out if your machine is IPv4-only - it should immediately<br>
fail for IPv6, and then try IPv4.<br>
<br>
What does "ip -6 route" show on your machine?<br>
<br>
I'd guess that your machine thinks it *does* have IPv6, because a friendly<br>
Windows box in the neighbourhood announced a 2002 prefix...<br>
<br>
*Broken* IPv6 is what causes these problems, "no IPv6" is handled just fine<br>
(but then, for outgoing mail sent by a MTA, 30 seconds delay do not *really*<br>
cause harm)<br>
<span class="HOEnZb"><font color="#888888"><br>
Gert Doering<br>
-- NetMaster<br>
--<br>
have you enabled IPv6 on something today...?<br>
<br>
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</font></span></blockquote></div><br>