Squid proxy pac file query

[Easy_506]

Hi all,

 

Just posting this on the off-chance there's someone on the forums who has the knowledge to feed back on our current PAC file we're utilising.

 

We have two virtual Squid proxies, one for staff the other for pupils. What I'm seeing a lot of is our pupil machines not being able to reach the proxy and then getting the classic IE 'This page cannot be displayed'. The problem is intermittent and occurs randomly.

 

Any thoughts on whether this looks ok are most welcome! Thanks in advance.

 

PAC:

 

function FindProxyForURL(url, host)

{

if (isInNet(myIpAddress(), "10.167.0.0", "255.255.0.0")) {

return "PROXY 10.160.2.6:8080";

}

 

return "PROXY 10.10.2.16:3128";

}

[FN-GM]

How are you pushing out the pac file?

 

THanks

[grant_girdwood]

Hi all,

 

Just posting this on the off-chance there's someone on the forums who has the knowledge to feed back on our current PAC file we're utilising.

 

We have two virtual Squid proxies, one for staff the other for pupils. What I'm seeing a lot of is our pupil machines not being able to reach the proxy and then getting the classic IE 'This page cannot be displayed'. The problem is intermittent and occurs randomly.

 

Any thoughts on whether this looks ok are most welcome! Thanks in advance.

 

PAC:

 

function FindProxyForURL(url, host)

{

if (isInNet(myIpAddress(), "10.167.0.0", "255.255.0.0")) {

return "PROXY 10.160.2.6:8080";

}

 

return "PROXY 10.10.2.16:3128";

}

 

As FN-GM has said it could be down to the way that the file is being pushed out, you'll want to watch out for automatic proxy caching in IE - http://support.microsoft.com/kb/271361

 

As an aside you'll find this tool very useful for testing your pac file syntax and rules - https://github.com/pacparser/pacparser

[Easy_506]

How are you pushing out the pac file?

 

THanks

 

Thanks for the replies. Pac file is being pushed out via GPO. It does seem that the GPO is applying itself to the machines fine, it's that point of contact with the proxy server (e.g. trying to reach Google on HTTPS) that you can have 30 PCs in a suite all hitting the same site simultaneously, and maybe 5-10 machines will not connect.

[grant_girdwood]

Is there any specific browser/OS that this is affecting or happening across multiple? If you're happy that the pac file is being applied correctly then it could be an issue with your squid proxy, you'll want to have a look through the squid logs to see if you can find any errors that show up when the users are experiencing this issue.

 

Wireshark on the client machine and tcpdumps on your squid proxy would be my next steps once I was happy the pac file is being applied correctly .

[Easy_506]

Is there any specific browser/OS that this is affecting or happening across multiple? If you're happy that the pac file is being applied correctly then it could be an issue with your squid proxy, you'll want to have a look through the squid logs to see if you can find any errors that show up when the users are experiencing this issue.

 

Wireshark on the client machine and tcpdumps on your squid proxy would be my next steps once I was happy the pac file is being applied correctly .

 

 

Thank you, I will start with your suggestions as I am happy there aren't any GPO failings so it must be the Squid proxies.

 

And sorry, yes these are all Win 7 32bit machines running IE10. Last year I was nice enough to let pupils use Chrome too, and I saw the same issue occur with both browsers.

Edited February 20, 2015 by Easy_506

[grant_girdwood]

Thank you, I will start with your suggestions as I am happy there aren't any GPO failings so it must be the Squid proxies.

 

I've fallen for that before, it could be an issue with the local device - the IE caching has caught me out a few times (http://support.microsoft.com/kb/271361) and another gotcha could be in IE11, SPDY support was added which can result with sites failing to load first time - could be an idea disabling SPDY in IE just in case this is causing the issue - https://msdn.microsoft.com/en-us/library/ie/dn265035(v=vs.85).aspx - try disabling SPDY/3 in advanced settings...

 

Hope this helps!

[Easy_506]

I've fallen for that before, it could be an issue with the local device - the IE caching has caught me out a few times (http://support.microsoft.com/kb/271361) and another gotcha could be in IE11, SPDY support was added which can result with sites failing to load first time - could be an idea disabling SPDY in IE just in case this is causing the issue - https://msdn.microsoft.com/en-us/library/ie/dn265035(v=vs.85).aspx - try disabling SPDY/3 in advanced settings...

 

Hope this helps!

 

At least now I've got some more ideas of things to look for, so something is better than nothing! Thanks very much for taking the time to write back.

[grant_girdwood]

At least now I've got some more ideas of things to look for, so something is better than nothing! Thanks very much for taking the time to write back.

 

No problem at all - would be good to hear how you get on - good luck!

 

Cheers!