How do I prevent NAT timeouts on idle SSH and telnet connections?
I’ve been able to verify that the BEFSR41 will tear down idle connections after 7200 seconds (2 hours). This is a fairly common practice with various brands of “personal” router/firewalls. The reason is that the router’s NAT (Network Address Translation) logic must maintain a table to keep track of each outgoing connection, and it doesn’t want this table to grow too large, so it will “reap” connections that have been idle for too long as a sort of “housekeeping” measure. Regardless of how justified this is, it can be quite annoying if, for example, you use ssh to stay logged in to your work, or are running a background job, etc. The bad news is that there is no way to change the timeout value or turn it off using the setup screens. The good news is that there are several different ways to defeat NAT timeouts. The first is to exploit “TCP KeepAlive”. All operating systems that have TCP/IP networking have the ability to send special packets at a certain interval to check if a connection
