To secure your system better by allowing selected hosts to ssh into your system as root, you will need the Match keyword found in the /etc/ssh/sshd_config
For example, to allow only 192.168.x to be able to ssh into the system, you do the following. If you are using
Edit the SSH Config
% vim /etc/ssh/sshd_config
1. By IP Addresses
PermitRootLogin no ..... ..... # Example of overriding settings on a per-user basis Match Address 192.168.*,172.21.1.1 PermitRootlogin yes
2. By Host Name
PermitRootLogin no UseDNS yes ..... ..... # Example of overriding settings on a per-user basis Match Host *.example.com,host1.idontknow.com PermitRootlogin yes
3. By User and IP Addresses
PermitRootLogin no UseDNS yes ..... ..... # Example of overriding settings on a per-user basis Match User user1 Host *.example.com PermitRootlogin yes
Restart SSH Service
% systemctl restart sshd.service