Thanks Aliaksandr,
I perform some additional test without involving any LAN device but only with the Router., and these are the results:
Test with CLI access to RUT950 in Firefox
1. 08:43 login
08:57 still connected, so force CLI exit
2. 09:13 login
09:15 Session closed
3. 09:16 login
09:22 Session closed
4. 09:23 login
09:25 Session closed
5. 09:26 restart CLI from RMS
09:27 login
09:28 Session closed
6. 09:29 login
09:35 still connected
09:38 Session closed
7. 10:36 login
10:37 Session closed
8. 10:38 login
10:45 still connected - force CLI exit
9. 10:46 login
10:47 Session closed
As you can see the behaviour is quite unstable, if you could try to repeat the test with your router I think it could help to understand if the issue is only related to my router or is more general.
Thanks,
Gianluigi