Logging method Logged by IP issues

Hi,

I recently built a WordPress-website and I installed the WP ULike Plugin as a post rating system. I set the logging method to log by IP. Now I’m experiencing some issues when different people try to vote from (let’s say) the same office (where they probably have the same IP throughout). When Person A votes on Post A and Person B (within the same office building) wants to vote on Post A as well, they see that a/their vote has already been cast, even though that isn’t the case. My website allows anyone (registered or not) to vote on my posts.

The questions that I have are:
Is it because of the ‘Logged by IP’-setting? If so, can I change the logging method during a voting period (without losing earlier votes)? And what Logging method would be better? If it’s not possible: is there any other kind of workaround?

Thanks in advance!