Strange Wireguard Issue - VPN Tunnel active but no traffic using public wlan

[wseifert]

I am volunteer at red cross and have sometimes 11 hour standby service on the base. So I use the waiting time to work with my laptop. We are provided with wlan there and so I use Wireguard on Windows 11 to connect to my home office running OPNsense FW (official ip address). This was working well for long time, since a few weeks I see a strange behavior: Connection to home office is good but no routing of ip packets, so no connection to host(s) possible. Only the tunnel addresses from my computer and from the vpn tunnel is possible to ping. The routing table is ok, an entry for the tunnel and my office network is availiable.

So I did some testing: Using my cell phone (tethering) connected directly to the internet (not using the wlan, not possible if using tethering) the vpn connection works, I can connect to hosts on my office network from my windows computer.
A bit more investigation showed me that the wlan network is using 10.0.0.0 address range to service wlan clients.
Any idea why this behavior occurs now?

Thanks in advance!
Werner

[Patrick M. Hausen]

Does your home network overlap with the address range on the WiFi?

[wseifert]

No, different Range: home network 192.168.0.0/24, tunnel 192.168.100.0/24, wifi 10.0.0.0/24

[wseifert]

Yesterday I tested OpenVPN instead of Wireguard, worked fine.
So for me Wireguard using high port and UDP has a problem in this case; I do not have information what internet router brand is used and if what firewall. Since Wireguard was working until end of last year and my config did not change and is working on other locations a config change or software update or something else on the wifi net is the reason for.