Pinging websites and MTU size

There are a couple of sites that I have problems visiting using IE 7. They
are www.tesco.com and www.chesterzoo.org
I was told by Tesco to lower the MTU to 1400 on my router but this hasn't
helped. I have no problems with the sites on Opera. The strange thing is
that if I try to ping these sites from the CMD screen I get a timed out
reply. If I try and ping any other sites I get a response. can anyone
suggest why this happens?
Thanks
Tony

 

Try the Tweak Test here (NOT for Vista!): http://www.dslreports.com/tools

 

Thanks for the tip. Tried it and didn't show any errors suggested up MTU to
1500 but I'm on ADSL and I think the max should be 1492?
Tony

 

Did you run DrTCP, too?
http://www.dslreports.com/drtcp

How to troubleshoot network connectivity problems in Internet Explorer
[ignore APPLIES TO section if you're not running Vista]
http://support.microsoft.com/kb/936211

 

Obviously those sites (or servers on the path to them) block ICMP.
Unfortunately the value of ping and tracert as diagnostics has been
greatly reduced as servers have taken defensive measures against
moronic "Denial Of Service exploits".

However, you might still be able to check if you have an MTU size problem
with a site by using tracert to find out where the ICMP starts being blocked.
Then just do the ping -f -l to the last server you do reach. Otherwise, you
will just have to use some other protocol than ICMP to do your tests with.

Good luck

Robert Aldwinckle
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