Hi, I'm hoping someone with more networking expertise can help me out here.  My original setup was a CM1000 cable modem connected to an Orbi RBR750 router with a Synology NAS on a local static IP address. I had a port forward rule in the Orbi to route ports 5005-5006 to 192.168.1.200.  And that worked fine.

I modified my network to include an M6 Nighthawk for failover and revised the configuration this way:  I have the CM1000 and M6 ethernets connecting to an ER605 WAN ports, then the LAN connection to the Orbi.  That is working well, but i cannot access the Synology from outside the local network.

I added a virtual server NAT rule to route 5005-5006 to 192.168.1.200  (which did not work) and I also tried routing it to 192.168.1.1 (the gateway address of the Orbi -- thinking the Orbi could then reroute the connection to the Synology), but that did not work either.  I also tried disabling port forwarding on the Orbi, but that didn't help

I have the ER605 v2.0 and just upgraded to the latest firmware 20231017.  I'm assuming I have an issue with addressing or something else is bllocking the connection.  Any advice on what to try next?

Thanks!