Resolving macOS VPN error "The L2TP-VPN server did not respond. Try reconnecting."
When connecting to the Northwestern VPN using the native macOS VPN client, you may receive the error "The L2TP-VPN server did not respond." This usually occurs when something is blocking the VPN connection from completing, such as using an incorrect preshared key or trying to connect on a restricted public network or in a country with a national firewall (like China). See below for ways to fix this error.
Feinberg School of Medicine members should contact FSM IT at firstname.lastname@example.org for assistance with any VPN errors.
Use Cisco AnyConnect instead
Northwestern IT recommends using Cisco AnyConnect to connect to the VPN on macOS; most VPN errors such as this one do not occur when using the Cisco client instead. See this Knowledge Base article for instructions to set up Cisco AnyConnect.
Check the Shared Secret key
If the preshared key was entered incorrectly, the VPN connection will not respond. The preshared key for the Northwestern vpn is northwesternvpn ; make sure it is entered correctly in the VPN settings of the Network window in System Preferences. See this Knowledge Base article for configuration instructions.
Make sure your network is not blocking L2TP ports
If you are connecting on a home or private network, this error will appear if your router is not allowing network traffic through certain ports. The Nortwestern VPN requires UDP ports 500, 1701, and 4500 to be open to function; make sure any firewalls on your computer or router do not block these ports. Consult your router's or firewall software's documentation for instruction on opening these ports, or contact your network administrator for help; Northwestern IT cannot help configure networks not operated by the University. Some Internet service providers may not allow VPN connections; contact your ISP if you feel this may be the case.
A public network and/or country's firewall may block the VPN connection
Many public networks and all networks in countries with restrictive national firewalls (including the People's Republic of China and other countries with state-operated internet filtering) may block L2TP-VPN connections. Using the Cisco AnyConnect client may get around this restriction.