Re: [squid-users] TCP_MISS/503 0 CONNECT errors

From: Bruno Santos <>
Date: Mon, 02 Jul 2012 09:28:24 +0100 (WEST)

Hi Amos,

thank you for the reply.

I don't have IPV6 on my network and i've disabled CentOS IPv6 :

cat /etc/sysconfig/network:

I'm using CentOS 5.8 and the last squid i can find using yum is this one i'm using: squid- - although yum (when trying to upgrade) says i've installed squid-2.6.STABLE21-6.el6.

I'm going to further study and try to solve this issues with yum and squid.

In my DNS (bind-9.3.6) i've disabled IPv6 name resolution... (i was getting a lot of errors in /var/log/messages). Can this have something to do? Should i enable IPv6 in bind ?

Thank you


Bruno Santos

----- Original Message -----
From: "Amos Jeffries" <>
Sent: Saturday, 30 June, 2012 9:17:45 AM
Subject: Re: [squid-users] TCP_MISS/503 0 CONNECT errors

On 30/06/2012 1:30 a.m., Bruno Santos wrote:
> Hi all.
> I've search in the internet and i've done some experiences with some solutions i found on the internet, but still no luck.

First hint: you are still using a *beta* release of Squid-3.1. That
series has been in stable releases for over 2 years.

NP: I advise using no release older than 3.1.15. There are major
security vulnerabilities in all older releases.

Second hint: that 503 status generated by Squid means no destination
could be contacted. ie the TCP connection setup failed. "Error 111
(net::ERR_TUNNEL_CONNECTION_FAILED): Unknown error." is Chrome
"user-friendly" display the 503 failure status.

  DNS resolution of AAAA and A records failed (no destination able to be
  TCP connection to some found IPv6 address(es) failed
  TCP connection to some found IPv4 address(es) failed

NP: the problem is very likely to be your IPv6 connectivity or some IPv6
issue in that 3.1 beta release. Google services are mostly IPv6-enabled
and using HTTPS (via CONNECT) since earlier this month. Squid-3.1 will
try very hard to connect using IPv6 whenever possible.


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Received on Mon Jul 02 2012 - 08:28:46 MDT

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