problem opening some websites with some machines

[Wendy.J]

Our network of approximately 30 machines is connected to the ADSL Internet
provider using a gateway machine. The connection is shared using WinRoute.
Just recently, some machines are unable to open one or two web sites. We
have a backup ISP which is also ADSL and if I switch over to the other ISP,
then all machines can access the problem web sites. I called the ISP and
they tell me to change the DNS settings to an updated DNS server. I did this
although it seemed rather pointless because even though the machines would
not access the problem web sites, an NSlookup resolved to the correct IP. I
should mention that the gateway machine also is one of the machines which
cannot open the problem sites when connected to our main ISP. This problem
only occurred recently so it makes me wonder if the ISP has changed
something perhaps to do with a downstream proxy? This is just a stab in the
dark about welcome any advice which anybody has. I have checked for spyware
and all machines are current with Norton anti-virus. All machines are
running Win2K and the firewall is turned off for the testing of this
problem.

 

[-keevill-]

Our network of approximately 30 machines is connected to the ADSL
Internet provider using a gateway machine. The connection is shared
using WinRoute. Just recently, some machines are unable to open one
or two web sites. We have a backup ISP which is also ADSL and if I
switch over to the other ISP, then all machines can access the
problem web sites. I called the ISP and they tell me to change the
DNS settings to an updated DNS server. I did this although it seemed
rather pointless because even though the machines would not access
the problem web sites, an NSlookup resolved to the correct IP. I
should mention that the gateway machine also is one of the machines
which cannot open the problem sites when connected to our main ISP.
This problem only occurred recently so it makes me wonder if the ISP
has changed something perhaps to do with a downstream proxy? This is
just a stab in the dark about welcome any advice which anybody has. I
have checked for spyware and all machines are current with Norton
anti-virus. All machines are running Win2K and the firewall is turned
off for the testing of this problem.

This could be the MTU setting. Check the MTU setting on the machines which
are able to access the websites and see if the default has been changed to
something other than the default. do a google search for 'change mtu setting
win2k' and you will find plenty of resources on this. Post back if you need
help on this.
-keevill-