Ssh is not working correctly, how to fix it?

Question

linux

There is a server with the ssh port configured on the 3000th. And port forwarding from the outside to this server. There is access to the server from the outside, but in the local network access appears only after the server itself 'refers' to the machine - you need to ping the machine from the server, for example.
Moreover, the machine cannot ping the server - it says that the node was not found. On the contrary, everything works. Router zte521 (yes, GPON), debian server

Answer 1

iptables -L -v -n -t natto the studio
andcat /etc/ssh/sshd_config | sed '/#/d'