Can you please provide some guidance how to set up my RUTX11 (192.168.11.1) as DHCP relay, so its clients (Raspberry Pi 4, phone, tablet) receive their IPs from my AVM FritzBox 7490 (DHCP server)?
The 7490 (192.168.178.1) is my gateway at home and serves all my clients their IPs. Even my RUTX11 is entered in the 7490’s network/ DHCP table with its MAC address, but if that helps, I don’t know (as the RUTX11 currently has a static IP from another IP range - see also below).
The RUTX11 is in my motor home and connected (also when away from home) to my 7490 via mobile network or public WiFi and WireGuard. A Raspberry Pi 4 is connected to the RUTX11 via ethernet cable. Further devices connected via WiFi to my RUTX11 are my phone and tablet.
My goal is that all my devices (incl. Raspberry Pi 4, phone, and tablet) always have unchanged IPs when connected to the 7490 or to the RUTX11.
I think that this is possible via DHCP relay but don’t know how to proceed.
To configure DHCP relay, navigate to Network → Interfaces → Edit LAN → Under DHCP server, switch from ‘enable’ to ‘relay’.
Alternatively, you can assign static leases by going to Network → Interfaces → Static leases. This ensures that specified devices consistently receive their designated IP addresses from the RUTX11’s DHCP.
However, it seems that you want to have a single network. I would suggest using a layer2 VPN, such as OpenVPN in TAP mode or L2TP over IPSec. This way, devices on both, FritzBox and RUTX11 LANs would be on the same subnet (for example, 192.168.11.0/24). Configuration examples are available here and here, respectively.
Wireguard is layer 3. Thus, the LAN subnets would need to be different on the RUTX11 and FritzBox for routing to work. You can try following the configuration examples in the links I hava provided and try OpenVPN or L2TP over IPSec, depending on what is available of FritzBox.
