RV340 dual WAN router cannot detect WAN failure when behind NAT

[nimrody]

Our RV340 is connected to two ISPs for redundancy. Each ISP had supplied us with a modem (actually a simple consumer grade wireless router) that is configured to work as a NAT.

The router is connected to both modems receiving addresses 11.100.101.1 and 12.100.101.1 from their built in DHCP servers and serving using its own DHCP server the range 10.100.101.x to the internal LAN.

The problem is that the router fails to detect when one of the WAN links fail since the link to the modem is always on. Is there any way to make the router "ping" a remote address or similar to reliably detect WAN failure?

The two modems cannot work in "bridge" mode and are controlled by the ISPs.

[ktonev · Accepted solution]

Hi nimrody,

You are correct, the RV will be unable to detect that a WAN link is down by default as it is monitoring the link state which will continue to stay up. You can modify this option if you go to WAN -> Multi-WAN -> Select WAN1 -> Adv. Config -> Enable Network Service Detection -> Remote Host and enter something like 8.8.8.8 (Google DNS). 

The default option there is "Default Gateway" so essentially the RV will be pinging the LAN interface on the modem which will almost always be up unless you physically damage the link or turn off the modem.

Thanks,
Kris

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