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Knowledge document #687

Cannot establish a VPN connection between two FRITZ!Box networks

The VPN connection between two FRITZ!Box networks is not established. One of the following error messages may be displayed in the event log of the FRITZ!Box attempting to establish the VPN connection:

  • "IKE-Error 0x1c"
  • "IKE-Error 0x2005"
  • "IKE-Error 0x2020"
  • "IKE-Error 0x2027"

Simply proceed as described below. After each measure, check whether the problem is solved.

Note:All instructions on configuration and settings given in this guide refer to the latest FRITZ!OS for the FRITZ!Box.

1 FRITZ!Box is not accessible on the internet

You can only establish a VPN connection between two FRITZ!Boxes if at least one of the two FRITZ!Boxes has an IPv6 or IPv4 address that is accessible on the internet. If both of the FRITZ!Boxes only have a private IPv4 address, it is not possible to establish VPN connections.

You can determine whether the FRITZ!Boxes have an IP address that is accessible on the internet using the guide Checking accessibility of the FRITZ!Box in the internet.

Note:If you use MyFRITZ!, you can also check the IP addresses of your FRITZ!Boxes from on the go in the Device Overview of your MyFRITZ! account at myfritz.net in the section "Device Overview for Your MyFRITZ! Account".

2 Permanently maintaining the internet connection of the remote FRITZ!Box

To ensure that the remote FRITZ!Box is always reachable, configure it so that it permanently maintains the internet connection:

  1. Open the user interface of the FRITZ!Box you want to establish the VPN connection to.
  2. Click "Internet" and then "Account Information" or "Type of Connection".
  3. Click "Change connection settings".
  4. Enable the option "Maintain permanently (recommended for flat rates)". If the option is not shown, the FRITZ!Box is already permanently connected to the internet.
  5. Click "Apply" to save the settings.

3 Internet connection of the remote FRITZ!Box is disrupted

  1. Open the user interface of the FRITZ!Box you want to establish the VPN connection to.
  2. Click "System" and then "Event Log".
  3. Select "Internet Connection" from the drop-down list.
  4. If you find error messages such as "DSL not responding" or "PPPoE error" that correspond to your attempts to establish a VPN connection, resolve the problems with the remote FRITZ!Box's internet connection. If necessary, consult your internet service provider.

4 MyFRITZ! address of the remote FRITZ!Box cannot be reached

If the VPN connection occasionally cannot be established, there may be an issue with the MyFRITZ! service. Therefore, check whether the FRITZ!Box to which the VPN connection should be established is successfully registered with MyFRITZ! when you try to establish the VPN connection:

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Online Monitor" in the "Internet" menu.
  3. If MyFRITZ! is active, continue with the next section.
    • If MyFRITZ! is displayed as not active, wait until the technical issues have been resolved and try to establish the VPN connection at a later time. If the error is permanent, reconfigure the MyFRITZ! account.

5 Correcting the internet address of the remote FRITZ!Box

If you connected two FRITZ!Box networks via IPSec (LAN-LAN linkup), check the MyFRITZ! address of the remote FRITZ!Box:

  1. Click "Internet" in the FRITZ!Box user interface.
  2. Click "Permit Access" in the "Internet" menu.
  3. Click the "VPN (IPSec)" tab.
  4. Click the (Edit) button next to the respective VPN connection.
  5. Enter the MyFRITZ! address of the remote FRITZ!Box (kw23qbmnj31x5aw75.myfritz.net) in the field "Web address".

    Note:The MyFRITZ! address is displayed under "Internet > MyFRITZ! Account" in the section "MyFRITZ! Internet Access " of the user interface of the remote FRITZ!Box.

  6. 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.

6 Adjusting the VPN settings

If you connected two FRITZ!Box networks via IPSec and only one of the FRITZ!Boxes has a public IP address, the option "Hold VPN connection permanently" may only be enabled in the FRITZ!Box with the private IP address:

Adjusting the VPN settings in the FRITZ!Box with a public IP address

  1. Open the user interface of the FRITZ!Box with a public IP address.
  2. Click "Internet" and then "Permit Access".
  3. Click the "VPN (IPSec)" tab.
  4. Click the (Edit) button next to the respective VPN connection.
  5. Disable the option "Hold VPN connection permanently".
  6. Enter the password required to establish the VPN connection in the field "VPN password (pre-shared key)".
  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.

Adjusting the VPN settings in the FRITZ!Box with a private IP address

  1. Open the user interface of the FRITZ!Box that does not have a public IP address.
  2. Click "Internet" and then "Permit Access".
  3. Click the "VPN (IPSec)" tab.
  4. Click the (Edit) button next to the respective VPN connection.
  5. Enable the option "Hold VPN connection permanently".
  6. Enter the password required to establish the VPN connection in the field "VPN password (pre-shared key)".
  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.

7 Attempting to connect to the remote network at a later time

This section only applies if the VPN connection occasionally cannot be established and the message "IKE-Error 0x2020" is displayed in the event log of one of the FRITZ!Boxes:

When one of the FRITZ!Boxes is working at high capacity while attempting to establish a VPN connection (for example when copying large volumes of data to FRITZ!NAS), an error may occur when synchronizing the VPN passwords (preshared keys). In this case the VPN connection cannot be established.

In this case, try accessing the shared files or services in the remote FRITZ!Box network at a later time. The VPN connection is automatically re-established whenever a query is sent from the network of one FRITZ!Box to a device in the network of the other FRITZ!Box.

8 Deleting a VPN connection and reconfiguring it

If the VPN connection cannot be established at all, the VPN settings in one or both of the FRITZ!Boxes are incorrect. Therefore, reconfigure the VPN connection:

  1. Delete the VPN connection in the user interface of both of the FRITZ!Boxes.
  2. Either use IPSec or WireGuard to reconfigure the VPN connection between the two FRITZ!Boxes.
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