The port map time can be altered to clear the TCP NAT session more frequently in DrayTek routers. The default TCP timeout is 86400sec which is 24hrs.

How to adjust NAT session timeout value?

When a session is initiated, the router will add a dynamic entry for the address and port mapping. NAT session timeout is the length of time that the router still keeps that entry even if the session is inactive. After that, the entry will be removed and the incoming packets will not be sent to internal IP anymore. Vigor Router has different default timeout value for each application, the value can be checked and configured by telnet command “portmaptime”.

Check the current value

By telnet command “portmaptime -l”, we can check the current value for each application.

 

Adjust the timeout value

To change the NAT timeout value, enter command “portmaptime -[protocol] [time]”, where [protocol] is a character represents the application (please use command “portmaptime ?” to check the options available), and [time] is a number of seconds. For example, if you’d like to set the timeout value of UDP session to 5 minutes (300 seconds), this can be done by the command “portmaptime -u 300”.

After that, you may use the command “portmaptime -l” to check if the current value has changed.