Is there a way to ping a client on the LAN side of a GL-AXT1800 from my system on the WAN side, using some type of Port Forwarding, or 1:1 NATing or some special LuCI firewall setting? I know ICMP doesn't use "ports", but I understand some routers have a mechanism to bounce ICMPs between the two Class C subnets on either side of itself.
Even though in my understanding this makes absolutely no sense, a possible solution is:
Admin panel -> System -> Advanced
Login into the LuCI panel
Child Network -> Firewall
Choose Tab "Port Forwards", click the button [Add], and choose as protocol 'ICMP'. Add a rememberable name for the rule and set the internal IP address.
Confirm with the button [Save].
Short explanation, why I doubt this will be useful: for a internal device behind a route, that is not local, you generally want to check if a service is up. Services normally don't work at ICMP level. So all checks should be better be performed on the service, not on local management features.
Some routers and firewalls even close the ICMP answer 'for security'. I don't think the so called "stealth mode" is a good countermeasure against an attack either, but I would not forward this into my secured LAN.
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