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Knowledge document #3712

FRITZ!Box reports "The configured WireGuard remote site caused a network conflict"

When you try to configure a WireGuard connection in the FRITZ!Box, the following error message is displayed:

"Unfortunately, it was not possible to apply your settings.
The configured WireGuard remote site caused a network conflict.
Click on 'Close' to go to the WireGuard overview and set up the WireGuard connection again".

Cause

  • The FRITZ!Box cannot configure the WireGuard connection because the new connection would cause a conflict with the WireGuard connections that are already configured.

1 The FRITZ!Box already sends all network traffic over another VPN connection

If the option "Send all IPv4 network traffic via the VPN connection" is enabled for a WireGuard connection in the FRITZ!Box, then the FRITZ!Box sends all web requests to the VPN remote site, regardless of whether the VPN remote site is a different FRITZ!Box, a VPN provider, or a smartphone. Since the FRITZ!Box can only send its network traffic to a single remote site, this option can only be enabled for one WireGuard connection.

Example:
The FRITZ!Box can send all its network traffic either to only one VPN provider or only to a remote FRITZ!Box, but not to both at the same time.

If you want the FRITZ!Box to send all of its network traffic to a VPN remote site other than the one already configured, delete the existing WireGuard connection.

2 IP network 192.168.180.0 is being used

The FRITZ!Box prevents you from configuring WireGuard connections for the IP network 192.168.180.0 (subnet mask 255.255.255.0) because this IP network is used by the FRITZ!Box itself in some configurations.

If one of the two FRITZ!Boxes uses the IP network 192.168.180.0, configure a different IP network in the FRITZ!Box:

Changing the FRITZ!Box's IP network
  1. Click "Home Network" in the FRITZ!Box user interface.
  2. Click on "Network" in the "Home Network" menu.
  3. Click on the "Network Settings" tab.
  4. Click "Additional Settings" in the section "LAN Settings" to display all of the settings.
  5. Click the "IPv4 Settings" button.
  6. Enter the desired IP address and subnet mask.

    Important:Do not enter an IP address from the network 192.168.100.x. In compliance with DOCSIS, this network is reserved for the cable provider and may not be used in the FRITZ!Box.

  7. Click "Apply" to save the settings and on the FRITZ!Box, confirm that the procedure may be executed, if you are asked to do so.

3 Remote IP network is already being used

For WireGuard connections between two FRITZ!Box networks or the FRITZ!Box and another router (LAN-LAN linkup), both sides must use different IP networks. VPN communication is not possible if both sides use the same IP network. The remote IP network must therefore be different from the FRITZ!Box's home network and guest access and may not be used for other LAN-LAN linkups that are already configured in the FRITZ!Box.

If the IP network of the new VPN remote site is already used by the FRITZ!Box or a different VPN remote side, either change the IP address of the new VPN remote site or the IP address of the FRITZ!Box.

Note:You can determine the IP networks used by the FRITZ!Box for the home network and guest access under "Home Network > Network > Network Settings > IPv4 Settings".

4 Remote router uses IP address other than x.x.x.1

If the remote router uses a different IP address within the IP network (for example 192.168.20.199) instead of the first IP address of the IP network (for example 192.168.20.1), then this IP address (192.168.20.199) must be entered in the "Remote network" field in the FRITZ!Box when configuring LAN-LAN linkup.

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