Limit vote to one per IP Address

You many have to do a pre-check prior to storing the votes.

The votingapi table contains the IP address and the content_id that you can use to for the precheck

something like

1) query the votingapi to get the ip address and content_id
2) Do an If check criteria comparison between the current IP and whats stored in the database)
something like ( if browser IP = stored IP and content_id = the current contend_id )
// abort
else (

// store vote

hope that helps