[PLUG] Re-establishing ICMP ping Capability

[Tim]

>    I've no idea what to change to let others ping my IP address. It should be
> possible as I have no reason to block that service. I don't see that service
> specifically listed in the Netgear's service list; I suppose that I could
> try adding it if I know whether it used UDP or TCP and what ports would be
> appropriate.


ICMP doesn't use TCP or UDP, it is a sibling protocol at the same
layer.  It doesn't use ports either.  Ports are an implementation
detail of both TCP and UDP which just happen to coincide and are often
standardized together, but in IP itself, there's no such thing as
ports.

Instead, ICMP uses a set of message types.  For ping, the messages are
called "echo request" and "echo reply" or something there abouts.
Many other message types exist besides this, some of which are
critical for a properly functioning network connection.

The ability to be ping-ed should not be affected by DNS.  It is almost
certainly an issue with your Netgear router or with your Linux host's
configuration.  tcpdump would be useful in detecting whether or not
echo request packets are making it through the netgear.

HTH,
tim