Setting your RWIN and MTU settings in Windows Server 2003

Situation:

You get timeouts or no connection when browsing websites or generally connecting to other things.

Problem:

First you have to rule out any DNS problems.  On your server, you should only have 127.0.0.1 in your TCP/IP DNS properties.  You add the ISP DNS numbers in the forwarders tab in the DNS MMC snap-in and also delete the root hints for the "." zone.  That is well documented on Microsoft's site.  Go to a cmd prompt and run nslookup.  Enter a workstation name.  ie. station1.  It should resolve.  Next, try an internet site that you can't reach.  If it resolves, you don't have a DNS problem.  In this case, you need to lower the MTU settings on your server.

Solution:

See this Microsoft Article ID 900926 and look at Method 3 for an explanation of how to change the MTU for a particular network card.  You can also look at my other page on how to use ping to determine the correct MTU size.

Also make sure your adminstator has not blocked ICMP packets at the firewall or from your workstation. This causes the MTU Path Discovery to fail.

Last updated December 12, 2006.

Jeff Borders