Hello everyone,

I am using a FritzBOX 6690 as a modem (with IPv4 address, no DS Lite), my ER707 is behind it (no exposed host), port forwarding in the FritzBox is set. Only the router is connected to the FritzBox, no other device (not even via WLAN). I manage the router via Omada.

I currently have the following problem: I normally connect to my home network via OpenVPN (the ER707 is my VPN server) when I have appointments in the field. This has worked without any problems so far. I wasn't traveling much at the end of November and in December, so I only noticed this now: The OpenVPN connection could no longer be established. I did update the firmware on the router once during this time, but that was it.

I have now tested the following:

- Does the DynDNS resolution work? Yes, the FritzBox does the DynDNS update at duckdns - the update works

- As a test, I connected a fresh Raspberry with only a web server directly to the LAN of the FritzBOX to test the port forwarding function in general -> call with the dyndns address -> works immediately

- deleted all port forwardings on the FritzBox, restarted the FritzBox, set up the forwardings again -> no change

- Switched to Exposed Host as a test -> no change

- connected the Raspberry web server to the router and set port forwarding -> not accessible

When I start the OpenVPN connection with my Android client, the log looks like this:

[Jan. 18, 2024, 17:02:21] OpenVPN core 3.git::081bfebe:RelWithDebInfo android arm64 64-bit PT_PROXY
[Jan. 18, 2024, 17:02:21] ----- OpenVPN Start -----
[Jan. 18, 2024, 17:02:21] EVENT: CORE_THREAD_ACTIVE
[Jan. 18, 2024, 17:02:21] Frame=512/2048/512 mssfix-ctrl=1250
[Jan. 18, 2024, 17:02:21] EVENT: RESOLVE
[Jan. 18, 2024, 17:02:21] Contacting 178.27.XXX.XXX:1194 via UDP
[Jan. 18, 2024, 17:02:21] EVENT: WAIT
[Jan. 18, 2024, 17:02:21] Connecting to [XXXXXXXXXX.duckdns org]:1194 (178.27.XXX.XXX) via UDPv4 

Unfortunately I can't find any logs for the firewall on Omada, it feels like one setting doesn't match - but I haven't made any changes to the system in the last few weeks apart from the firmware update.

As we say in german: "I probably can't see the wood because of all the trees" :-)