Hi All !

I'm facing to some monitoring problem and I'd welcome any ideas. 

Situation: 

Location #1:    Omada ER605 - Primary Cable internet and with 4G Dongle as backup link

Location #2:    Omada ER706W - Primary Cable internet and with 4G Dongle as backup link

Wireguard S2S VPN between the two. 

I have only these two omada devices I'm not using OC200 or the Cloud based controller since I can easily manage these two in the standalone web interface. 

I have installed Cacti monitoring in both Locations to monitor the other location via SNMP and to report if the other side router is down. 

But I have just realized that since I have the 4G dongles in both Cacti will never recognize the router as down as the routers are doing the failover to the 4G.

I couldn't find any SNMP MIBs either for the ER605 or the ER706W  therefore  I can't monitor the individual WAN link status since only standard SNMP things are working like Ping latency polling...etc to the router.

So the question is what would be the best way to get an alert if the primary WAN connection is down, without any controller in the network ? 

Or can I somehow control the Wireguard S2S VPN to work only through the Primary connection and not throught he 4G and therefore if the S2S VPN is down then despite the 4G failover the Other side Cacti will see the router Down and then let's say I can login over OpenVPN through the failover 4G to see what's going on. 

Any ideas are welcome.