One of my devices (WIRED connection with local IP 192.168.0.139) connected to my RT-AC56U ROUTER hangs after 4 or 5 hours of inactivity. The only way to make the device work again is to REBOOT the router, e.g. with ssh [email protected] reboot command, after which 192.168.0.139 works fine again (router is 192.168.0.2).

The only problem is that the reboot takes a LOT of time, and I want to access 192.168.0.139 faster/instantaneously. Is there a SSH command(s) of resetting/remapping the network without having to reboot the router itself, so that stale/inactive/corruptly configured devices are configured again. I have SSH root access to the router also over the internet.

Just for INFO: the device 192.168.0.139 is always visible with its mac address in the 'arp' table even when it becomes non-responsive, and also adding it again with arp -s 192.168.0.139 does not help.
so rebooting the device doesn't help, only rebooting the router?i don't have an option to reboot the device over the internet when I am away from home. I can access my router over ssh though.