TCP/IP Network Traceroute

Traceroute is a utility that records the route (the specific gateway computers at each hop) through the Internet between your computer and a specified destination computer. It also calculates and displays the amount of time each hop took. Traceroute is a handy tool both for understanding where problems are in the Internet network and for getting a detailed sense of the Internet itself.

When you enter the traceroute command, the utility initiates the sending of a packet (using the Internet Control Message Protocol or ICMP), including in the packet a time limit value (known as the "time to live" (TTL) that is designed to be exceeded by the first router that receives it, which will return a Time Exceeded message. This enables traceroute to determine the time required for the hop to the first router. Increasing the time limit value, it resends the packet so that it will reach the second router in the path to the destination, which returns another Time Exceeded message, and so forth. Traceroute determines when the packet has reached the destination by including a port number that is outside the normal range. When it's received, a Port Unreachable message is returned, enabling traceroute to measure the time length of the final hop. As the tracerouting progresses, the records are displayed for you hop by hop. Actually, each hop is measured three times. (If you see an asterisk (*), this indicates a hop that exceeded some limit.)

Understanding the results:

The first column is the hop number, which is the Time-To-Live (TTL) value set in the packet.

Each of the next three columns contains the round-trip times in milliseconds for an attempt to reach the destination with the TTL value.

The fourth column is the host name (if it was resolved) and IP address of the responding system.

In the results you will see the comment, "over a maximum of 30 hops". All this means is that the diameter of the Internet is roughly 30 hops and, therefore, many trace routes will only go that far out in trying to reach a destination.

An asterisk, "*", followed by the words "request timed out" is not out of the ordinary. If the tracert had stopped here and continued to respond with "request timed out", then it might have been indicative of a problem.

Generally, a response time of less than 500 milliseconds is considered acceptable.

See also:

• http://www.thecaretaker.org.uk/tracert.htm

Get a tracert back to you from other servers:

• http://www.tracert.com/cgi-bin/trace.pl very nice! From multiple servers around the world.
• http://network-tools.com/default.asp?prog=trace&Netnic=whois.arin.net
• http://www.dnsstuff.com/tools/tracert.ch?ip=

Some sample tracert's to mail.efplus.com

  2     9 ms     9 ms     9 ms  adsl-68-249-3-254.dsl.milwwi.ameritech.net [68.249.3.254]
  3    11 ms    11 ms    10 ms  dist2-vlan60.milwwi.ameritech.net [65.43.19.243]
  4    11 ms    11 ms    10 ms  bb1-g2-0.milwwi.ameritech.net [65.43.19.115]
  5    13 ms    13 ms    13 ms  bb1-p3-2.chcgil.ameritech.net [151.164.190.85]
  6    14 ms    13 ms    13 ms  bb2-p11-0.chcgil.ameritech.net [151.164.191.182]
  7    16 ms    15 ms    14 ms  ex1-p3-0.eqchil.sbcglobal.net [151.164.188.162]
  8    14 ms    14 ms    14 ms  ex2-p11-0.eqchil.sbcglobal.net [151.164.40.126]
  9    14 ms    15 ms    14 ms  sl-st20-chi-0-0.sprintlink.net [144.223.241.57]
 10    15 ms    14 ms    15 ms  so-2-1-0.edge1.Chicago1.Level3.net [209.0.225.21]
 11    15 ms    15 ms    16 ms  so-2-1-0.bbr1.Chicago1.Level3.net [209.244.8.9]
 12    78 ms    79 ms    78 ms  ae-0-0.bbr1.LosAngeles1.Level3.net [64.159.1.125]
 13    78 ms    77 ms    78 ms  so-8-0.core1.LosAngeles2.Level3.net [64.159.4.30]
 14    78 ms    76 ms    77 ms  4.68.115.146
 15    76 ms    76 ms    75 ms  4.68.115.70
 16    80 ms    80 ms    80 ms  a-7-0-4.lsanca1-ar11.bbnplanet.net [4.24.45.38]
 17   109 ms   109 ms   358 ms  mail.efplus.com [66.13.172.18]

When your firewall or ISP will not allow ICMP:
traceroute to 66.13.172.18 (66.13.172.18), 30 hops max, 40 byte packets
 1  dslrouter (192.168.1.1)  1.143 ms  0.54 ms  0.475 ms
 2  * * *
 3  * * *
 4  * * *
 5  * * *
 6  * * *
 7  * * *
 8  * * *
 9  * * *
10  * * *
11  * * *
12  * * *
13  * * *
14  * * *
15  * * *

This person can NOT access the web site, but the tracert is just fine
1 1 ms 1 ms 1 ms 192.168.2.1 
2 28 ms 28 ms 28 ms 10.4.8.1 
3 27 ms 27 ms 27 ms 130.81.10.149 
4 31 ms 31 ms 31 ms 130.81.18.12 
5 30 ms 30 ms 31 ms 130.81.10.90 
6 30 ms 31 ms 30 ms 67.29.172.13 
7 31 ms 30 ms 30 ms 209.244.11.9 
8 102 ms 103 ms 103 ms 64.159.1.157 
9 103 ms 103 ms 103 ms 64.159.4.26 
10 103 ms 103 ms 103 ms 4.68.115.146 
11 103 ms 416 ms 102 ms 4.68.115.66 
12 103 ms 102 ms 102 ms 4.24.45.38 
13 136 ms 137 ms 136 ms 66.13.172.18

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