traceroute not responding

Hi,

A have two of our staff who cannot access our server from home, however
most can. When I asked that they do a traceroute to see if packets are
getting to the server, I noticed (using tcmdump) that the ICMP packets
are not being echoed back. The same person using www.network-tools.com
can get through OK.

Now, I've checked the firewall and cannot see any blocking being done.
These people used to be able to access our server up to recently and
now without any changes made cannot do so.

My question is, does any body know under what circumstances the ICMP
protocol would not respond to a ping or traceroute packet?

My server is running ClerckConnect distro which is redhat 9.0.

Any help would be greatly appreciated.


Thanks

In news:(E-Mail Removed) oups.com,
gpao <(E-Mail Removed)> wrote:

> My question is, does any body know under what circumstances the ICMP
> protocol would not respond to a ping or traceroute packet?

If the ISP blocks it, as was/is commonly done to disable the effects of some
MS virus that was rampant some time ago.

It's more reliable (and generally far more useful in a lot of ways) to use
http://freshmeat.net/projects/tcptraceroute/ as one can target specific
ports on the remote machine with informative results, other than the default
port 80.

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gpao wrote:
> Hi,
>
> A have two of our staff who cannot access our server from home, however
> most can. When I asked that they do a traceroute to see if packets are
> getting to the server, I noticed (using tcmdump) that the ICMP packets
> are not being echoed back. The same person using www.network-tools.com
> can get through OK.
>
> Now, I've checked the firewall and cannot see any blocking being done.
> These people used to be able to access our server up to recently and
> now without any changes made cannot do so.
>
> My question is, does any body know under what circumstances the ICMP
> protocol would not respond to a ping or traceroute packet?
>
> My server is running ClerckConnect distro which is redhat 9.0.
>
> Any help would be greatly appreciated.
>
>
> Thanks
>

Some cable routers block ICMP traffic. Some windows firewall products
block ICMP. Traceroute on some linux boxes use UDP by default.


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