I have two sites.. both running Telstra Business Smart Modems (V7610) with V18.104.22.168 firmware. Both are configured in the webconsole to respond to ICMP (ping).
One responds... one doesnt.
So either :
a) Telstra blocks ICMP on SOME connections before they hit the end point.
b) Re-Badged Netgear Tesltra Modem's are garbage and their configs can be corrupted with no recourse (ive seen this with other model netgears.. and the only answer was replace of the device with different model).
This may also explain other peoples issues with VPN and Port Forwarding.
I have three sites using these devices and this firmware, They respond to ping for a period after a reboot but then stop... the port forwarding fails totally. When i called (and was on the phone for 1 hour) and got one downgraded to .26 it automatically upgraded over night... going to try and disable ip v6 and see if they helps