I've been curious how many of the 435 registered
gateways were reachable,
so I collected ICMP unreachable messages during a recent RIP transmission
(which of course sends to every gateway) and got the following:
33 gateways aren't reachable or are rejecting inbound IPIP packets
I think it would be a good idea to somehow keep track of this information and remove
or at least mark inactive those gateways for which this condition persists
for some amount of time. Especially when protocol 4 is rejected.
Host unreachable could be because the internet is down or the power is out,
but an explicit protocol 4 rejected indicates nonexistent configuration, that
could temporarily exist because e.g. new system has just been installed that has
not been configured yet, but should not persist for longer than say 2 weeks.
The operator can alwayes re-enable or re-add the gateway when he has found the
opportunity to re-install it.
Rob