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360 CHAPTER 12: USING SYSTEM MANAGEMENT COMMANDS
Description
Use the tracert command to check the reachability of network connection and
troubleshoot the network. User can test gateways passed by the packets
transmitted from the host to the destination.
By default, when the parameters are not specified,
first-TTL is 1,
max-TTL is 30,
port is 33434,
nqueries is 3 and
timeout is 5s.
The tracert command sends a packet with TTL 1, and the first hop will send an
ICMP error message back to indicate this packet cannot be transmitted (because
of TTL timeout). Then this packet will be sent again with TTL 2, and the second
hop will indicate a TTL timeout error. Perform this operation repeatedly till
reaching the destination. These processes are operated to record the source
address of each ICMP TTL timeout so as to provide a path to the destination for an
IP packet.
After the ping command finds some error on the network, perform tracert to
locate the error.
The output of the tracert command includes IP address of all the gateways to
the destination. If a certain gateway times out, output "***".
Example
Test the gateways passed by the packets to the destination host at 18.26.0.115.
<SW4500>tracert 18.26.0.115
tracert to allspice.lcs.mit.edu (18.26.0.115), 30 hops max
1 helios.ee.lbl.gov (128.3.112.1) 0 ms 0 ms 0 ms
2 lilac-dmc.Berkeley.EDU (128.32.216.1) 19 ms 19 ms 19 ms
3 lilac-dmc.Berkeley.EDU (128.32.216.1) 39 ms 19 ms 19 ms
4 ccngw-ner-cc.Berkeley.EDU (128.32.136.23) 19 ms 39 ms 39 ms
5 ccn-nerif22.Berkeley.EDU (128.32.168.22) 20 ms 39 ms 39 ms
6 128.32.197.4 (128.32.197.4) 59 ms 119 ms 39 ms
7 131.119.2.5 (131.119.2.5) 59 ms 59 ms 39 ms
8 129.140.70.13 (129.140.70.13) 80 ms 79 ms 99 ms
9 129.140.71.6 (129.140.71.6) 139 ms 139 ms 159 ms
10 129.140.81.7 (129.140.81.7) 199 ms 180 ms 300 ms
11 129.140.72.17 (129.140.72.17) 300 ms 239 ms 239 ms
12 * * *
13 128.121.54.72 (128.121.54.72) 259 ms 499 ms 279 ms
14 * * *
15 * * *
16 * * *
17 * * *
18 ALLSPICE.LCS.MIT.EDU (18.26.0.115) 339 ms 279 ms 279 ms