WhatRoute is designed to find the names of all the routers an IP packet passes through on its way from your Mac to a destination host. It also measures the round-trip time from your Mac to the router, thus enabling you to determine slow links--or hops--in the Internet. WhatRoute can also find dead links, such as routers that don't respond.
Note: While the software is classified as free, it is actually donationware. Please consider making a donation to help support development.