Important This article contains information about how to modify the registry. Make sure to back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows registry
For a Microsoft Windows XP version of this article, see
314868.
SUMMARY
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
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
MORE INFORMATION
How the TRACERT Command Works
The 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 (157.54.48.1 and 11.1.0.67) to get to host 11.1.0.1. In this
example, the default gateway is 157.54.48.1 and the IP address of the router on
the 11.1.0.0 network is at 11.1.0.67.
C:\>tracert
11.1.0.1 Tracing route to 11.1.0.1 over a maximum of 30 hops
1 2 ms 3 ms 2 ms 157.54.48.1
2 75 ms 83 ms 88 ms 11.1.0.67
3 73 ms 79 ms 93 ms 11.1.0.1
Trace complete.
Troubleshooting with TRACERT
The 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 22.110.0.1. There is
probably a router configuration problem or the 22.110.0.0 network does not
exist (a bad IP address).
C:\>tracert 22.110.0.1
Tracing route to 22.110.0.1 over a maximum of 30 hops
1 157.54.48.1 reports: Destination net unreachable.
Trace complete.
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 Syntax
There are several command-line switches that can be used with
TRACERT, but they are usually not needed for standard troubleshooting.
TRACERT syntax:
tracert [-d] [-h maximum_hops]
[-j host-list] [-w timeout] target_name Parameters:
-d
Specifies to not resolve addresses to host names.
-h maximum_hops
Specifies the maximum number of hops to search for target.
-j host-list
Specifies loose source route along the host-list.
-w timeout
Waits the number of milliseconds specified by timeout for each
reply.
target_name
Name or IP address of the target host.
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
tracert HostName, you
find that the used path is as follows:
* <router1>
* <router2>
* <router3>
* <router4>
* <hostname>
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:
* <router1>
* <router2>
* <router3>
* <router4>
* <router3>
* <router2>
* <router1>
* <mycomputer>