This diagnostic utility determines the route taken to a destination by sending Internet Control Message Protocol (ICMP) echo packets with varying Time-To-Live (TTL) values to the destination. Each router along the path is required to decrement the TTL on a packet by at least 1 before forwarding it, so the TTL is effectively a hop count. When the TTL on a packet reaches 0, the router is supposed to send back an ICMP Time Exceeded message to the source system. Tracert determines the route by sending the first echo packet with a TTL of 1 and incrementing the TTL by 1 on each subsequent transmission until the target responds or the maximum TTL is reached. The route is determined by examining the ICMP Time Exceeded messages sent back by intermediate routers. Notice that some routers silently drop packets with expired time-to-live (TTLs) and will be invisible to tracert.
tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout] target_name
-d
Specifies not to resolve addresses to hostnames.
-h maximum_hops
Specifies maximum number of hops to search for target.
-j host-list
Specifies loose source route along host-list.
-w timeout
Waits the number of milliseconds specified by timeout for each reply.
The following shows sample output for tracert. The first column is the hop number, which is the Time To Live (TTL) value set in the packet. The next three columns are the round-trip times in milliseconds for three attempts to reach the destination with that TTL value. An asterisk (*) means that the attempt timed out. The fourth column is the hostname (if it was resolved) and IP address of the responding system.
/>tracert ds.internic.net
Tracing route to ds.internic.net [198.49.45.10]
over a maximum of 30 hops:
1 <10 ms <10 ms * [131.107.1.100]
2 10 ms <10 ms 10 ms seattle1-gw.nwnet.net [192.80.12.82]
3 * 10 ms 10 ms enss143-enet.nwnet.net [192.35.180.2]
4 20 ms * 10 ms t3-3.seattle-cnss8.t3.ans.net [140.222.88.4]
5 30 ms 30 ms 20 ms t3-0.los-angeles-cnss8.t3.ans.net [140.222.8.1
6 70 ms 70 ms 80 ms t3-0.new-york-cnss24.t3.ans.net [140.222.24.1]
7 80 ms 81 ms 80 ms t3-0.denver-cnss40.t3.ans.net [140.222.40.1]
8 100 ms 91 ms 90 ms t3-1.new-york-cnss32.t3.ans.net [140.222.32.2]
9 90 ms 90 ms 91 ms mf-0.new-york-cnss36.t3.ans.net [140.222.32.196]
10 100 ms 90 ms 91 ms t1-0.enss222.t3.ans.net [140.222.222.1]
11 140 ms 191 ms 100 ms ds.internic.net [198.49.45.10]
Trace complete.