Having a white hop means that hop has not responded in the number of samples defined by "Samples to include". If there's no IP in that hop at all, that means the hop has never responded - if there is an IP, then it has responded at least once, but not in the time window you've specified in "Samples to include".<br><br>As for the grey bar, this means that no data was sent to that hop during the time period it's grey. This is easily reproduced by hitting the stop button, waiting a while, then resuming. It can also happen, though, if the route changes - any new hops in the route have grey instead of red (because they didn't timeout, or respond - they just didn't exist in the route during that "grey" period).<br><br>Hope that helps. Feel free to e-mail me some graphs (or post them and link to a message here) if you want more clarification.<br><br>