Bit of an odd ones this...I have a 2860 situated in a property in Turkey. WAN1 is an ADSL connection, behind a carrier grade NAT. I use Remotix on a PC on the network and this lets me remotely open a VNC session into the network.

I also have a bridged 4G modem connected to WAN2. This has a static IP address which correctly shows up on the dashboard when it’s up.

I have setup port forwarding to a specific PC on the network which correctly allows me to connect to it via the WAN2 static IP address. I’ve verified this works and it’s clear it’s using the 4G connection as it is a much faster VNC session than when I connect using Remotix via the DSL.

I have set it up so that both WANs are always active but with no failover or aggregation or anything enabled. I have made it so that all outgoing routes use the DSL except a specific port number (for a hobby streaming project) uses the 4G WAN2.

Oddly I am finding that with this arrangement when WAN1 is down I can no longer connect into the network via WAN2. Am I missing something here that might explain this?

I first noticed this behaviour when I was at the location last. I’m not at the location right now but I know that there is power and I have remotely rebooted the router using a Technotrends Phoneswitch and I believe the DSL connection is down...but neither can I reach the network via WAN2.

I think the issue lies in your routing.

If all the routes are set to use WAN1 if this is down then they won't work. If you configure the routing failover (not forgetting the failback) to use WAN2 if WAN1 is down for the port(s) used this should solve the issue.

See Routing, Load Balance/Route Policy
Set to advanced mode as it's easier to see all the settings on a single page.

Also have you considered using a VPN dial up instead?