Set up one machine access to IP address

Hello everyone,

I have been trying to find this answer, and I am new to networking, so my search skills may be off.

I have an access rule configured in my router to allow specific port access to a specific IP within our network. This allows users to access the internal database through this host computer.

I set the host up with a static IP, but it had a power surge and another machine jumped onto its IP thus making the database unreachable.

I put the host on a battery backup, but is there a way to only allow a certain machine to connect to the IP? I checked in the router configuration, searched online, and searched here. I haven't found this yet. Also, everything is running Windows 7 or Windows 10.