IP address different to another system


Hi. I’m a newbie to Piwik and so far think it’s awesome. However, I’ve recently noticed a visitor with a different IP address showing in the visitor log to that shown in a different system also in use - chat. Is this something to do with Do Not Track being in effect in Piwik but not in the other system? I am sure it is the same visitor as we tracked it through several pages which were identical with same times. Thanks in anticipation.