On Wed, Sep 23, 2020 at 03:48:56PM -0400, Greg Wooledge wrote:
The normal reason people need to use ServerAlive or ClientAlive is NAT. If your connection from ssh client to ssh server goes through a NAT router, the router may keep track of activity on that connection, and drop the translation when it goes idle for 5 minutes or so. Forcing the *Alive packets to happen every few minutes prevents a NAT timeout.
This is a stateful firewall thing, not a NAT thing