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502 Proxy Error - 28.Feb.2008 10:45:39 AM

JJG323

Posts: 11
Joined: 6.Feb.2008
Status: offline

Hi, 2nd time poster on this site for a ISA problem and would appreciate the insight.

We have regular users who have webmail from our exchange front end server.

They go to https://mail.(ourcompany's domain name).com

When ever someone tries to access this in the field - in the offices - that we have and they do not have full internet access = going threw select sites in the ISA proxy and Surf Control they can not get access to the webmail website.

We know that it works, cause if we change the policy to take off the proxy, or try it externally from outside the domain, the page comes right up.

But from inside the domain I get this error:

Network Access Message. The page cannot be displayed.

Error code: 502 Proxy Error. The host was not found. (11001)
IP Address: (The address of our ISA server is displayed)
Date: (The date and time is shown but strangely enough the time is always 5hrs ahead. I check the ISA server and it has the correct time)
Server: (The name of the server which ISA resides on is displayed)
Source: proxy

What is going on here? Could this be a DNS error somewhere?

I have installed Service Packs I, II, III on ISA 2004 standard edition.
Also I have Service Pack I, and II of the Surf Control, and lots of updates
up to but not including SPII for Server 2003.

Thanks
J

Post #: 1

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RE: 502 Proxy Error - 28.Feb.2008 4:07:02 PM

Rotorblade

Posts: 1002
Joined: 27.Feb.2007
Status: offline

Hi J,

There are a few things I see possibly with your issue.

1. For internal requests, you do not want to be looping back through the ISA. You need to configure for direct access.

2. It does not appear that you're running a "Split DNS" where as the FQDN is not resolving internally.

HTH

RB

_____________________________

David Melvin
Ohio
MCSE: Security 2003, MCSA:Security 2003

(in reply to JJG323)

Post #: 2

RE: 502 Proxy Error - 29.Feb.2008 11:21:31 AM

JJG323

Posts: 11
Joined: 6.Feb.2008
Status: offline

How do i configure for it not to loop back to the ISA?
I thought they open up there browser with the IP address of the proxy server that they get in the policy of Active Directory.

Then the go where ever they want.
Most users have access for about 300 or so "approved" sites.
They do not have full interent access.

In their policy:
Bypass proxy server for local addresses is checked off, and port *8080 is selected.

Any suggestions?

I did try a rule in the ISA to allow the proxy server to the exchange server for web access, and a second rule that takes it fron the exchange server back to the isa.
Exactly the same problem resulted.

We are still getting the 502 error, and the time difference which is very strange.

Ideas, comments?

thanks
Joe

< Message edited by JJG323 -- 29.Feb.2008 11:23:22 AM >

(in reply to Rotorblade)

Post #: 3

RE: 502 Proxy Error - 29.Feb.2008 12:21:03 PM

Rotorblade

Posts: 1002
Joined: 27.Feb.2007
Status: offline

quote:

How do i configure for it not to loop back to the ISA?

There are a few ways to go about configuring depending on how you�re populating the Web proxy client information in the Web browser. You mentioned that you were pushing through AD GP and that you enabled the �Bypass Proxy for local access� option. Just enabling the bypass proxy option alone is not enough. You must also populate the local addresses and domains box with a list of addresses and domains that you want to bypass. This information can be set in GP and pushed to your clients.

The other option is to configure the ISA Web proxy property settings and use the Web proxy automatic discovery and configuration script. The article below may be of some help.

http://isaserver.org/articles/2004directaccessp1.html

From the error log, it appears that DNS is part of the problem. Probably due to a miss-DNS configuration if not due to the loopback issue. A quick test would be to uncheck the use Proxy server in IE and see if you can access your OWA site. If you can, then bypassing and not looping back through your ISA will fix the problem.

HTH

RB

_____________________________

David Melvin
Ohio
MCSE: Security 2003, MCSA:Security 2003

(in reply to JJG323)

Post #: 4

RE: 502 Proxy Error - 10.Mar.2008 3:43:43 PM

JJG323

Posts: 11
Joined: 6.Feb.2008
Status: offline

Hi,
I went it to the properties of the internal, and added in the domain name.
It was not set to bypass automatically anything within the domain.

thanks for the help
J

(in reply to Rotorblade)

Post #: 5