[BUG] connection to AVM FritzBox's wireguard fails.

[nuthub]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

This is a follow-up on the closed issue #391, which I can't comment on anymore.
In contrast to the closing comment of #391, the issue is related to wireguard, of course. Networking works perfectly fine otherwise. NAT is not involved in any way, the machine (proxmox VM) has its own dedicated public IP addresses. The same machine (proxmox VM) can connect to other wireguard servers from within a container, but not to a FritzBox Wireguard.

Expected Behavior

The wireguard tunnel should allow me to reach and ping hosts at the other side of the tunnel (FritzBox side).

Steps To Reproduce

see #391

Environment

- docker host OS: Debian 12.11 on a Proxmox VM with public IP address, networking works fine.
- Docker container was configured as described (but I also created manually an ubuntu derived container, and tried wg-quick, same behavior)

CPU architecture

x86-64

Docker creation

docker compose up --force-recreate

Container logs

[migrations] started
[migrations] no migrations found
───────────────────────────────────────

      ██╗     ███████╗██╗ ██████╗
      ██║     ██╔════╝██║██╔═══██╗
      ██║     ███████╗██║██║   ██║
      ██║     ╚════██║██║██║   ██║
      ███████╗███████║██║╚██████╔╝
      ╚══════╝╚══════╝╚═╝ ╚═════╝

   Brought to you by linuxserver.io
───────────────────────────────────────

To support the app dev(s) visit:
WireGuard: https://www.wireguard.com/donations/

To support LSIO projects visit:
https://www.linuxserver.io/donate/

───────────────────────────────────────
GID/UID
───────────────────────────────────────

User UID:    1000
User GID:    1000
───────────────────────────────────────
Linuxserver.io version: 1.0.20250521-r0-ls81
Build-date: 2025-07-29T17:05:49+00:00
───────────────────────────────────────

Uname info: Linux a8e182305a85 6.1.0-37-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.140-1 (2025-05-22) x86_64 GNU/Linux
**** As the wireguard module is already active you can remove the SYS_MODULE capability from your container run/compose. ****
****     If your host does not automatically load the iptables module, you may still need the SYS_MODULE capability.     ****
**** Client mode selected. ****
[custom-init] No custom files found, skipping...
**** Disabling CoreDNS ****
**** Found WG conf /config/wg_confs/wg_nuthome.conf, adding to list ****
**** Activating tunnel /config/wg_confs/wg_nuthome.conf ****
[#] ip link add dev wg_nuthome type wireguard
[#] wg setconf wg_nuthome /dev/fd/63
[#] ip -4 address add 192.168.178.203/24 dev wg_nuthome
[#] ip link set mtu 1420 up dev wg_nuthome
**** All tunnels are now active ****
[ls.io-init] done.
**** Disabling tunnel /config/wg_confs/wg_nuthome.conf ****
[#] ip link delete dev wg_nuthome

[nuthub]

The issue is limited to an AVM FritzBox Wireguard server. Connection to other Wireguard servers works with the same setup. Connection to the AVM Fritzox Wireguard server works outside of the docker container.

Cf #391 (comment)

[j0nnymoe]

Unfortunately we're limited in what we can test because I don't believe anyone within the team has access to fritzbox hardware. It might be due to something Fritz are doing with their setup of wireguard. It does feel like more of a Fritz issue than our container (happy to be proven otherwise) if you have no issues accessing it with out clients.

Might be worth contact Fritz directly?

[nuthub]

Might be worth contact Fritz directly?

see #391 (comment) (AVM is the vendor of FritzBoxes)

So, A sends me to B, B sends me to A. For sure, I know that this is a project driven by volunteers. Therefore, I'm not feeling like a customer expecting that someone solves the issue for me. Instead I'm trying to find persons that see the same issue(s) or no issue(s) with an equivalent setup (FritzBox-wireguard / docker-wireguard) and/or to find a person that helps me to narrow down the reason for this issue.

[LinuxServer-CI]

This issue has been automatically marked as stale because it has not had recent activity. This might be due to missing feedback from OP. It will be closed if no further activity occurs. Thank you for your contributions.

[nuthub]

Is there anything / any information that I can contribute? If this issue is closed, I probably won't find a person with a similar setup (see #396 (comment)).