Sporadic intranet problem

[LinkZ]

I am having an issue with students and teachers sometimes being unable to access intranet sites, when a user logs on and tries to access an intranet page they get the usual "Internet Explorer is unable to display this webpage" error page. The only way to correct it is to have the user log off then back on again. All external sites work during this time. It only seems to happen once maybe twice a day and we have hundreds of students log on every day.

 

There doesn't appear to be a pattern as to who it happens to or what machine it happens on, so I am unable to recreate it to test it, I just have to wait for it to happen to someone!

 

I have tried firefox portable when it happens and this is able to access all internal and external sites whilst IE continues not to work, so it must be a problem with internet explorer its self or one of the GPO's I have set.

 

Anyone have any ideas what it could be?

[pete]

Your "do not use proxy for these sites" settings aren't getting applied. And (as a second line of prevention) your proxy hasn't been told "hey, these are internal sites - just sent them straight there without filtering".

 

I suspect there's an issue with GPOs not being applied - use Resultant Set of Policy / Group Policy modelling in the Group Policy Management Console to test it.

 

Look in the application logs of an affected machine after the end-user experiences the issue for more info.

 

How are you currently setting your "don't use a proxy for these sites" exclusion list?

[ToyHeartsFan]

I would check your proxy exceptions as it sounds like they are not always being applied correctly for some reason hence external sites work but internal wont.

 

If these are XP workstations with gig nics then you need to disable media sensing otherwise your group policy settings dont always get applied.

[Dom_]

If you're in kirklees there seems to be an issue today with any sites that bypass the proxy.. waiting on a response.

[LinkZ]

Just had a closer look through my GPO's, it looks like there are a couple of conflicting settings to do with intranet sites zone and proxy bypass assignment in 2 GPO's that get applied to the users, changed these to be a bit more uniform, hopefully that will sort it.

 

Thanks for the ideas.

[newmoon1981]

Hi,

We are having a very similar problem at our school.. except, no sites, external or internal are accessible to only some 50computers dotted throughout the buildings.

The only work around seems to be logging off and on again, but there are some where they just dont work full stop.. could this be GPO also? thanks for any advice.

[ToyHeartsFan]

no sites, external or internal are accessible

 

Possibly but usually if the proxy settings are not applied to a PC you can normally still access internal sites (if an old invalid proxy address is being applied with no proxy exception rules for local sites that could cause the problem you are experiencing).

 

It could be a DNS issue (which can still be GPO related) have you tried to access your internal sites by ip address instead of server name on a PC that has the problem?

 

As I mentioned in my earlier post gigabit network connections can cause a problem if you are using XP, does this apply to you?

 

Another idea: Are all of the PCs you have a problem with connected to the same switch, if yes can you try patching a workstation into a different switch to see if that makes any difference.

[newmoon1981]

Hi,

 

thank you for your reply!

The proxy settings are configured through GPO, but the computers are different vintage, different ip networks (as in 192.1.x.x) and they are hanging off different switches.

The one other thing could be teh gigabit/XP problem you mention, but this only started happening last week! we've had this system in place for about 2yrs on XP!

[ToyHeartsFan]

If it is the XP gigabit nic problem (basically gpo doesnt always get applied) give this a go on one of the PCs

details

http://support.microsoft. com/kb/326152

 

work around

How to disable the Media Sensing feature for TCP/IP in Windows

(I use the registry entry on every XP workstation that has a gigabit nic.)

 

Have you tried opening internal / external sites by ip address (eg 207.46.197.32 = microsoft.com) if they open then it would suggest a dns issues rather than a proxy problem.

[LinkZ]

Just had a closer look through my GPO's, it looks like there are a couple of conflicting settings to do with intranet sites zone and proxy bypass assignment in 2 GPO's that get applied to the users, changed these to be a bit more uniform, hopefully that will sort it.

 

Thanks for the ideas.

 

Bumping my own post here after some further investigation.

 

I've checked the GPO settings for intranet sites to zone and proxy bypass, along with confirming the proxy settings are being set and this is all being done correctly.

 

I have noticed something new though, when the problem occurs it only happens with https sites. Any internal https site is unavailable however standard unsecured http works fine. External sites are available through https and http.