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

Danish Siddiqui wrote:
>
> Tek Bahadur Limbu wrote:
>> 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?
>>
> No, the only cable that is connected to the squid box is from the
> Sonicwall firewall.
>>> 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.
>>
> How will the script go. Can you give me some pointers till the time I
> look around for it.

Hi,

I think a simple script such as PING should suffice. If your 1st ISP
goes down, can you ping your Sonicwall Firewall WAN port?

>> 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.
>>
> Seems interesting to me too
>> If your Squid box is running on Linux with a kernel greater than
>> 2.4.20, then you can apply traffic and routing rules.
> Its running on a CentOS 4.4 with kernel 2.6.9-42.ELsmp
>> 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!
>>

Have you given any thoughts to implementing such a feature suggested by
lartc.org ?
I think it's ideal for your case where you have 3 internet providers
where you can split the load among the 3 providers?

Thanking you...

>>
>>> 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?
> Ill have to go according to your suggestions. But at the moment the
> squid box can access only 1 ISP line
>>> 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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>>
>
>
>
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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