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Prevent DNS Server service from utilizing port 4125, which breaks SBS2003 RWW

Posted on 2007-04-05
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Last Modified: 2010-04-01
I have a customer's Small Business Server which sometimes Remote Web Workplace stops working.

Using http://support.microsoft.com/kb/886209, and the command [ netstat -aon | find ":4125" ], I found that DNS.exe is utilizing port 4125.  Restarting the DNS Server service temporarily fixes the problem, but it may come back in a month or so.  (last few months the problem was fixed by rebooting the server until I dug a little deeper to pinpoint the problem)

The MS KB article explains how to stop the RPC service from not using that port... does anyone know of a way to stop DNS server from using that port also?
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Question by:JacksonTechnical
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by:AdamRobinson
ID: 18859491
If I'm not mistaken shouldn't your DNS server be using port 53?  

Have you tried re-configuring the DNS Server?
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by:Jeffrey Kane - TechSoEasy
ID: 18861793
DNS was using 4125?  Are you sure?  What made you think that?  

At any rate, you would still follow the steps outlined in the KB article to stop RPC from using port 4125 because even if it was DNS.exe, that service would not access the port directly, it'd use RPC.

Jeff
TechSoEasy
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by:JacksonTechnical
ID: 18862024
DNS was not configured to listen on any alternate ports.  I think it could have been an outgoing port connection to itself.  My netstat pipe find command prompt got closed or I would have posted the output.

To your question, "What made me think that" was the output from the netstat command and the PID matching the DNS service in task manager's process list.

We manage over 80 SBS servers, first time I've seen this.  But apparently it can happen... I'll go ahead and apply the RPC registry entries and hope for the best.

Also, FYI, for everyone else out there... SBS's RWW and it's port 4125 redirecting to 3389 on the end client machines does not listen like a normal port listening service.  It does not respond to a telnet prompt (no blank screen or anything), and it does not show up when you issue a NETSTAT command... but it is listening and does work when you forward your WAN traffic to it.  Just shows that a process can listen on a port and not register with normal tools to determine what is listening on what port.

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Jeffrey Kane - TechSoEasy earned 500 total points
ID: 18874660
That's true that 4125 wouldn't respond to a telnet request.  That's one of the security features of Small Business Server.  4125 will ONLY respond to the ActiveX encrypted request it receives while you are already connected via port 443.  It is otherwise not listening.

Jeff
TechSoEasy
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