This session will tell you how to restrict IP for your login system.
But you can only use this feature in google chrome.
1. Go to the 'Users' menu then the 'Group' sub menu
2. Choose which group you want to give restriction then give a check on the 'UserIPRestriction' role
3. Then set the IP that only allowed to login
by go to Setup menu → More Menu - Login Restriction
fill the IP in the 'Login IP Address' section at the bottom of this session according to your computer IP address