If you want to generate keys using SSH for automatic login / passwordless login then follow the steps

A -> your server where from you want to login remote servers
B, C servers you want to monitor
---------
- login to A
- ssh-keygen -t rsa
ENTER - ENTER - ENTER 
- chmod 600 $HOME/.ssh/id_rsa
- cat $HOME/.ssh/id_rsa.pub
- copy this into 1 line into $HOME/.ssh/authorized_keys file of server B and C.

It can be first time you have to login each server manually, but since 2nd try it login automatically.

=> you can copy the id_rsa.pub too with scp like this:
cd .ssh/
scp id_rsa.pub username@12.18.1.3:./authorized_keys