Re: [squid-users] Automatic switching of squid to a second internet link?

Danish Siddiqui wrote:
>
> Hi,
> Ive got squid proxy server running on a CentOS 4.4 machine. This proxy
> server is connected to the internet through a Sonicwall PRO3060
> firewall machine.
>
> We have got three different ISP lines, one of which is used by squid.
> All the three lines terminate at the firewall. One of these links then
> goes to the squid server.
> Many a times it happens that the internet link on the squid line goes
> down, because of which we have to switch the squid server on to one of
> the remaining ISP lines.

Hi Danish Siddiqui,

When the 1st ISP goes down, does that mean that you actually have to
switch the cable from your squid box to the 2nd or 3rd ISP link on your
Sonicwall machine?

>
> I was planning a setup in which an extra NIC would be attached to the
> squid server. This NIC would be connected to a different ISP line, so
> that when one link goes down, the squid proxy server automatically
> switches on to the next line, wherein the LAN users dont get to feel
> the difference while browsing. Also, when the original link gets
> restored, the squid server automatically switches back on to the
> original link

If your Sonicwall firewall and routing policy allows you to access all 3
ISPs lines from your Squid box, I think that you can use the
"tcp_outgoing_address" parameter to switch to either the 2nd or 3rd ISP
connection when the 1st ISP goes down.

Of course, you must have a small script in Crontab to check for internet
connectivity to your 1st ISP at regular intervals, say every 2 minutes.

If the 1st ISP gets internet connectivity again, then let the script
restore connectivity from the 2nd or 3rd ISP back to the 1st ISP again.

But again, adding 2 extra NIC cards to your Squid box will provide you
more control and fail over. In my opinion, it will be a very interesting
option.

If your Squid box is running on Linux with a kernel greater than 2.4.20,
then you can apply traffic and routing rules.

Please see the following link:

http://lartc.org/howto/lartc.rpdb.multiple-links.html

This guys really seem to perform some kind of magic with advanced
routing and traffic control!

>
> My current setup requires me to deny access to the squid server till
> the time it is up again.

I suppose that you can't access all 3 ISPs lines from your Squid box?

>
> Is this setup possible? And if yes, can you please tell me how or
> point me to the necessary resources.

I definitely think it is possible. Let's wait and get more help and
input from other experts and professionals from the Squid mailing list.

Thanking you...

>
> Thanks
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-- 
With best regards and good wishes,
Yours sincerely,
Tek Bahadur Limbu
(TAG/TDG Group)
Jwl Systems Department
Worldlink Communications Pvt. Ltd.
Jawalakhel, Nepal
http://www.wlink.com.np