The TRACERT (Trace Route) command is a route-tracing utility used to determine the path that an IP packet has taken to reach a destination.
Note You can run this utitily by typing tracert
IPAddress or tracert
HostName at the command prompt.
This article discusses the following topics:
- How the TRACERT command works
- Troubleshooting with TRACERT
- TRACERT syntax
How the TRACERT Command WorksThe TRACERT diagnostic utility determines the route taken to a destination by sending Internet Control Message Protocol (ICMP) echo packets with varying IP 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 should send an ICMP Time Exceeded message back to the source computer.
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. Note that some routers silently drop packets with expired TTLs and are invisible to TRACERT.
TRACERT prints out an ordered list of the routers in the path that returned the ICMP Time Exceeded message. If the -d switch is used (telling TRACERT not to perform a DNS lookup on each IP address), the IP address of the near- side interface of the routers is reported.
In the following example, the packet must travel through two routers (126.96.36.199 and 188.8.131.52) to get to host 184.108.40.206. In this example, the default gateway is 220.127.116.11 and the IP address of the router on the 18.104.22.168 network is at 22.214.171.124.
Tracing route to 126.96.36.199 over a maximum of 30 hops
1 2 ms 3 ms 2 ms 188.8.131.52
2 75 ms 83 ms 88 ms 184.108.40.206
3 73 ms 79 ms 93 ms 220.127.116.11
Troubleshooting with TRACERTThe TRACERT command can be used to determine where a packet stopped on the network. In the following example, the default gateway has determined that there is not a valid path for the host on 18.104.22.168. There is probably a router configuration problem or the 22.214.171.124 network does not exist (a bad IP address).
Tracing route to 126.96.36.199 over a maximum of 30 hops
1 188.8.131.52 reports: Destination net unreachable.
TRACERT is useful for troubleshooting large networks where several paths can be taken to arrive at the same point, or where many intermediate systems (routers or bridges) are involved.
TRACERT SyntaxThere are several command-line switches that can be used with TRACERT, but they are usually not needed for standard troubleshooting.
tracert [-d] [-h maximum_hops] [-j host-list] [-w timeout] target_name
You can use the -j option to force the outgoing datagram to pass through a specific router. To use the -j option in this manner, use the IP source route option. For example, if you type
Specifies to not resolve addresses to host names.
Specifies the maximum number of hops to search for target.
Specifies loose source route along the host-list.
Waits the number of milliseconds specified by timeout for each
Name or IP address of the target host.
tracert HostName, you find that the used path is as follows:
To find the path to router4 and back to the computer, type tracert -j <router4> <MyComputer>.
The path to router4 and back to the computer is traced. In this example, the path is typically the following:
Article ID: 162326 - Last Review: Mar 15, 2008 - Revision: 1