The default starting port in UNIX traceroute is 33434. This comes from 32768 (2^15, or the max value of a signed 16-bit integer) + 666 (the mark of Satan). Thank you to Richard Steenbergen of nLayer Communications, Inc. for today's fun fact! You can learn more about traceroute, the deceptively simple and easy to misunderstand diagnostic tool, from Mr Steenbergen's presentation notes on the subject here .