Hi! 

I recently upgraded my ER605 to the v2.4.5 Build 20260721 Rel.81048 and it stopped working. I had to reset it and troubleshoot, that's when I noticed that everything stopped working every time I connected the WAN port to my ISP's router. For some reason the ER605 adopts the IP assigned on the other router (192.168.100.254) and ignores its own IP (192.168.0.1). After connecting WAN I can't ping any other IPs on the 192.168.0.0/24 subnet, only devices on the other subnet. Somehow DHCP can lease addresses, but I still can't ping the gateway.

Just to be clear, I ran a factory reset, so no other changes other than connecting WAN and setting it with Dynamic IP. The ER605 should keep its 192.168.0.1 address as it had before, but instead adopts the 192.168.100.254 address, and if I disconnect the WAN, the router becomes inaccessible.

I don't know what else to try, this setup was working fine until it randomly failed after updating.