I am trying to restrict root access to 2 IP addresses and of course to localhost. All other machines cannot login to the machine through root user.

I am logged into 4 machines:
user0@192.168.1.100
user1@192.168.1.101
user2@192.168.1.102
user3@192.168.1.103

I should only be allowed to type in ssh root@192.168.1.100 from user3@192.168.1.103 and user2@192.168.1.102.

I tried putting this in /etc/security/access.conf:
+ : root : 192.168.1.102 192.168.1.103
- : root : ALL

But I still can't login root@192.168.1.100 from 192.168.1.102 and 192.168.1.103.

1. Are the above 2 lines correct?
2. What should they be if they are wrong.

I am using Redhat Linux 7.3

I'm on really shakey ground here, but is /etc/security/access.conf even relevant for ssh? I have my specific ssh allowed users, etc in /etc/ssh/sshd_config

Can you show me how to configure the sshd_config file.

From user1@192.168.1.101, a bash script logs in root@192.168.1.100 to change file permisions such as owner, group in the latter server.
But audit says you should not log in remotely as root, so I was wondering what the solution should be? From user1@192.168.1.101, perhaps I can log in as user0@192.168.1.100 then I will have to figure how to su - root without entering the password.

To avoid remote doing login as root, login as normal user then either:

1. su -
which will take you to root user (need root passwd)
or
2. sudo su -
which will take into root, need your normal user passwd
for this you need to use visudo to setup sudo file first.