RW>->>  RW> answer, I decided to re-install Win95 and see if that worked
RW>->> (to see if
RW>->>  RW> it was some quirk in Windows TCP/IP implementation).  Well,
RW>->> I was able
RW>->>  RW> to connect to the sites in question just fine with Win95!
RW>->> So, I assume
RW>->>  RW> something must be wrong with my installation of NT.  I try
RW>->> various
RW> DS> You are correct about the NT installation and some routers along
RW> DS> the path. What you're experiencing is called "black hole
RW> DS> routing". It happens when there are variations in MTU size along
RW> DS> the path.
RW> DS> By default NT is designed not to fragment IP packets and it must
RW> DS> be told to do so. The most common flaw is that somewhere along
RW> DS> the route from the host to the destination a larger MTU size is
RW> DS> in use. NT servers can't fragment the packets unless a registry
RW> DS> change is implemented at the host.
RW> DS> You can test this theory yourself by using ping and adjusting
RW> DS> the packet size downward from the default. At some point you'll
RW> DS> be unable to ping even local routers. Fixes to this issue are
RW> DS> posted in URL's at Microsofts site and you'll find them by
RW> DS> searching for "black hole router". Sometimes the problem needs
RW> DS> to be fixed at the host and the webmaster at each site needs to
RW> DS> know the problem exists.
RW>Well, I found the info on the MS site (EnablePMTUBHDetect set to 1),
RW>but I still have the same problems....:(  It sounds EXACTLY like what
RW>is happening, but there must be some other problem somewhere.
RW>When I do a ping to some of these sites (www.weather.com is one that
RW>hasn't work since I upgraded to NT), sometimes I get "destination net
RW>unreachable". This sounds like a routing problem to me, but for the
RW>life of me, I don't know what the problem could be.  My route tables
RW>are VERY simple.  The only route that I have added manually is the
RW>one to enable RAS to route packets, because I have wcPPP installed.
RW>I don't believe this is the problem, since my other NT machine is the
RW>same way, and it doesn't have wcPPP installed on it.
RW>Any more suggestions?
RW>Thanks much!
Rob,
I just checked this morning and I cannot reach www.weather.com either 
via ping or traceroute and we are an ISP. The traceroute stops at MCI in 
Atlanta. However, port 80, web serives are getting through.  This may be 
sitting behind a firewall.   One thing to remember is that many websites 
and ISPs are starting to filter a lot of UDP types of functions (i.e. 
ping etc..).  This often makes troubleshooting more difficult.
Jeff
CMPQwk 1.42 9999
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