@Clive_A Thank you for your thoughts. I've tried on 2 Windows 10 machines with 2 browsers (Edge, including incognito, and Firefox). Here is an example (same for other subnets I have defined): Indeed,...

With the newest Firmware Version: 2.3.0 Build 20250428 Rel.18967 for my ER605 v2.0, in the menu Status/Traffic Statistics/IP Statistics, each IP address in the selected subnet is shown multiple times...

Sorry for this old topic and maybe I'm wrong, but if all you want the machines in the 10.10.0.0/24 network access the Internet, you might try set the PPPoE option in Router A, then set the router B...