Troubleshoot Unstable VPN

If the VPN tunnel disconnects frequently, you may take the following steps to troubleshoot.

Make sure the WAN connection is stable

VPN is established through the Internet connection; therefore, it will be unstable if the WAN connection of one of the VPN Routers is not stable. Go to Online Status page to check the Up Time of both VPN Routers' WAN interface to see if this is the problem.

Enable "Always On" for Dial-out profiles (VPN clients)

For LAN-to-LAN profiles, the Idle Timeout is set to 300 seconds by default. It means the router will disconnect the VPN connection if it did not detect any traffic over the VPN connection for 300 seconds. If you don't want the VPN to be disconnected, enable "Always on" for Dial-out profiles.

Set "Idle Timeout" to 0 for Dial-in profiles (VPN server)

Similarly, If you don't want the VPN server to disconnect the connection for not detecting traffic, set "Idle Timeout" to 0.

Disable "PING to Keep Alive"

“Ping to Keep Alive” option is using ping to detect if the IPsec connection is alive or not. If the Ping Target IP is not responding Ping, IPsec VPN connection will drop every 60 seconds. Since most Vigor Routers support Dead Peer Detection(DPD) to detect IPsec connection, it is recommended NOT to enable the Ping to Keep Alive option if you are having VPN disconnecting problem.

Check if the IKE Key Lifetime setting is the same on both VPN routers

If the IPsec VPN disconnects on a certain interval, e.g. 1 hour, the disconnection may be due to an IPsec Re-key failure. An IPsec Re-key failure could be caused by the mismatched Key Lifetime setting on both VPN routers. Please use the same key lifetime setting on Vigor Router and the remote VPN server. If the disconnection still occurs at the key renew time, we may configure the lifetime to a shorter one for a try.

Ensure the battery is enough on the VPN client computers

Battery-powered computers may experience unexpected VPN disconnects when the operating system starts saving power for applications. Please plug in the power cord and see if it can stabilize the VPN connection.

Contact Support

If none of the above improve the VPN connection stability, please provide the information below to [email protected] for further analysis:
1. Remote Access to both Vigor Routers: Enable "Allow management from the Internet" via  and provide both Vigor Router's WAN IP, HTTP Port and Login Password for our technical support to access your router.
2. The Syslog on both Vigor Routers until the VPN disconnection occurs.
3. If the VPN client is DrayTek Smart VPN client, please provide the draytek_svc.log which can be found in the installation folder.