Network Address Translation (NAT) allows you to share a single public IP address with computers and devices on your network. In certain environments, you may wish to configure your AirPort Device to allow access to L2TP VPN Servers which are using private addresses. Setting this port configuration attempts to redirect IKE via UDP port 500 and ESP-UDP via UDP port 4500, which may conflict with Back to My Mac.*
If you wish to enable NAT port forwarding to L2TP VPN servers at private addresses on your AirPort base station, first ensure that the Back to My Mac service is disabled in AirPort Utility. If you configure NAT port forwarding to L2TP VPN servers at private addresses with Back to My Mac enabled, the setting for port forwarding to the servers will be ignored.
*As of July 1, 2019, Back to My Mac service is no longer available.
How to disable Back to My Mac for AirPort base stations
Make sure you are on the same local area network as the AirPort base station that you wish to configure. These instructions apply to AirPort Utility 6.0 or later.
- For OS X: In the Finder, choose Utilities from the Go menu, then open AirPort Utility. (As mentioned, you should be using AirPort Utility 6.0 or later).
For Windows, select Start > All Programs > AirPort, and open AirPort Utility. (As mentioned, you should be using AirPort Utility 6.0 or later).
- Select your AirPort Base Station, then click "Edit".
- Enter the AirPort base station password if prompted (not your Back to My Mac password).
- Click the "Base Station" tab if not already selected, then select all accounts from "Back to My Mac" and click the minus button, one at a time.
- Click Update to save your changes.