[TriLUG] Wierd Network Problem - Clues Appreciated

[Scott Chilcote]

Hi Folks,

One of the systems on my LAN started dropping packets really bad when I 
tried communicating with machines out on the internet.  Pinging sites 
like yahoo and ibiblio would return 3 out of 7,  2 out of 10, etc. and 
TCP connections (email, web) just timed out.

I tried two other machines on the same LAN, and they had no problems 
communicating with systems on the internet.  This seemed to rule out the 
broadband router and DSL modem.

The next thing I tried was replacing the NIC and the ethernet cable on 
the problem machine.  This turned out to make no improvement.  Then it 
occurred to me to try pinging other systems on the LAN with this one, 
and that worked just fine.  I put the old NIC back in, and it still 
worked fine.  It's only getting out to the internet with this system 
that isn't working.  I even tried it with a webserver running on a local 
system, and the web page came up fine.

I then started wondering if there was a problem with one of the ethernet 
connections on the DSL/Router/Switch or one of the other switches, so I 
tried changing those around.  This made no difference.

I've more or less ruled out an OS or configuration problem on this 
machine, too.  It's a dual-boot system with Win98se on one partition. 
The behavior is identical under Win98se.  There have been no recent 
configuration changes to this system other than adding a USB connected 
UPS.  I haven't tried removing that, but I guess it's worth doing.

Another symptom happens when I try to bring up the SMC DSL Router's 
administration web page.  The other systems can bring this page up 
instantly.  The "problem" system takes forever to bring it up, and it 
draws in a tiny piece at a time.  It did this even after I swapped out 
the NIC and the ethernet cable.  This happens even though pings sent to 
this LAN address return just fine.  This sort of indicates a TCP problem.

Has anyone seen this kind of behavior, or can you suggest something else 
to try?  I'm guessing there's something wierd going on inside the 
hardware of the faulty system, or there's a bizarre problem with the DSL 
router that makes it single out this one machine.  I hate to blow $100 
on a replacement DSL router if it isn't actually bad.

Thanks for any help!

                            Scott C.