Anonymous users on the same subnet

Hi,

Thank for this module. However, I have this problem and need help.

I allow anonymous users to vote on node of type advance_poll. So in the same company which users belong to a LAN and access internet through 1 public IP.

The problem is if one of the users, the rest can't vote. The result shows to them. This is because that they have the same IP.

Is there a way to use identity anonymous users through cookies which unique?

Thanks
Truyenle