Traceroute

Traceroute is a (typically Unix) TCP/IP utility which allows the user to determine the route packets take to reach a particular host. Traceroute works by increasing the "time to live" value of each successive packet sent, the first packet has a TTL value of one the second two and so on. When a packet passes through a router the router decrements the TTL vaule by one and forwards the packet onwards to the next hop. When a packet with a TTL of one reaches a router or other packet forwarding device like a firewall, the router discards the packet and sends an ICMP time exceeded (type 11) packet to the sender. The traceroute utility uses these returning packets to produce a list of routers that the packets have traversed en route to the destination host.

On modern Linux ditributions the traceroute utility uses UDP datagrams with a port number of 33434. Windows uses ICMP echo request (type 8) better known as ping packets.

On Microsoft Windows traceroute is implemented as tracert.

Example

Estonia to the United States. 195.80.96.219 (kauge.aso.ee) to 130.94.122.199 (larousse.wikipedia.org).

1   kauge.aso.ee
2   et-gw.aso.ee
3   kjj-bb2-fe-0-1-4.ee.estpak.ee
4   noe-bb2-ge-0-0-0-1.ee.estpak.ee
5   s-b3-pos0-3.telia.net
6   s-bb1-pos1-2-0.telia.net
7   adm-bb1-pos1-1-0.telia.net
8   adm-b1-pos2-0.telia.net
9   p4-1-2-0.r00.amstnl02.nl.bb.verio.net
10  p4-0-3-0.r01.amstnl02.nl.bb.verio.net
11  p4-0-1-0.r80.nwrknj01.us.bb.verio.net
12  p4-0-3-0.r00.nwrknj01.us.bb.verio.net
13  p16-0-1-1.r20.mlpsca01.us.bb.verio.net
14  xe-1-2-0.r21.mlpsca01.us.bb.verio.net
15  xe-0-2-0.r21.snjsca04.us.bb.verio.net
16  p64-0-0-0.r21.lsanca01.us.bb.verio.net
17  p16-3-0-0.r01.sndgca01.us.bb.verio.net
18  ge-1-2.a03.sndgca01.us.da.verio.net
19  larousse.wikipedia.org

• RFC792