Re: [squid-users] With 2 NICs NATed, how's squid working without tcp_outgoing_address?

On 7/05/2013 3:59 a.m., Joel Chen wrote:
> I have a simple CentOS 6.4 server setup with 2 NICs, eth1 hooks to the
> Cable Modem, eth2 hooks to the internal network at 10.10.10.1 and is
> NATed. I setup squid3 using the default config file and modified the
> few items such as localnet IP etc, and then point the browser on a
> machine connected to the 10.xxx network to use squid, but I can't get
> anything until I added a tcp_outgoing_address eth1_ip_address entry to
> squid config. Otherwise Squid returned connection failed error. I
> looked around many tutorials and examples and it seems others don't
> need tcp_outgoing_address unless they want to do some kind of
> balancing etc.
>
> I have no trouble reaching outside on my server with other programs,
> such as the browser. So I wonder how squid is working for others
> without the tcp_outgoing_address while it doesn't work on my setup.
> What enables squid to be able to reach the outside using the IP that's
> connected to the NATed LAN?

Squid is just like any other software, it opens a socket and lets the OS
decide what IP address to send from (usually the box pimary address).
The OS routing systems then take over and decide how the packet will
reach the destination Squid was connecting to.

For that to go wrong you have to have broken the OS packet routing
systems. You said NAT was in use, so there and the routing table are the
places to look. Please contact your OS firewall vendor for more help.
This is nothing to do with Squid.

Amos
Received on Tue May 07 2013 - 02:38:06 MDT