Trace Route

Trace Route (called traceroute under UNIX and tracert under Windows) is a very useful tool for analyzing network behavior and isolating problems. It determines the path that your TCP/IP packets take to a given destination, entered as an IP address or domain name. The results are fairly straightforward.

Here is a completed trace from www.cs.cf.ac.uk to www.stairways.com:

Hop Result Min Avg Max   Ip            Name
1	3/3	0.001	0.002	0.004	131.251.1.42	mr1-e0.cf.ac.uk
2	3/3	0.010	0.034	0.076	194.83.178.17	c7000.cf.welshman.net.uk
3	2/3	0.006	0.008	0.010	146.97.252.93	welshnet.bristol-core.ja.net
4	3/3	0.015	0.017	0.019	146.97.252.190	ext-gw6.ja.net
5	3/3	0.012	0.017	0.023	193.63.94.95	us-gw3.ja.net
6	3/3	0.083	0.093	0.108	193.62.157.18	ny-pop.ja.net
7	3/3	0.088	0.090	0.094	207.45.196.141	if-8-2.core1.newyork.teleglobe.net
8	2/3	0.076	0.077	0.079	207.45.223.110	if-10-0.bb8.newyork.teleglobe.net
9	3/3	0.081	0.084	0.088	207.45.198.74	ix-8-0-1.bb8.newyork.teleglobe.net
10	3/3	0.083	0.087	0.092	152.63.22.218	518.at-6-0-0.xr1.nyc9.alter.net
11	3/3	0.083	0.087	0.090	152.63.20.66	181.at-2-0-0.tr1.nyc8.alter.net
12	3/3	0.192	0.200	0.206	152.63.5.214	124.at-6-0-0.tr1.por3.alter.net
13	3/3	0.189	0.192	0.198	152.63.104.253	297.atm6-0.xr1.sea1.alter.net
14	3/3	0.204	0.208	0.211	146.188.200.41	195.atm7-0.gw1.sea1.alter.net
15	3/3	0.163	0.164	0.166	137.39.136.6	ixa-gw.customer.alter.net
16	3/3	0.226	0.233	0.237	63.237.224.54	
17	3/3	0.233	0.250	0.273	199.254.168.243

Here is a trace from www.cs.cf.ac.uk to www.netscape.com (Compare to trace earlier in notes (Trace here taken Sept 2000 earlier trace (Sept 1998)):

1	3/3	0.001	0.001	0.002	131.251.1.42	mr1-e0.cf.ac.uk
2	3/3	0.012	0.028	0.041	194.83.178.17	c7000.cf.welshman.net.uk
3	3/3	0.008	0.010	0.012	146.97.252.93	welshnet.bristol-core.ja.net
4	3/3	0.009	0.017	0.029	146.97.252.61	bristol.south-east-gw.ja.net
5	3/3	0.012	0.015	0.021	193.63.94.240	uk-gw.ja.net
6	3/3	0.008	0.012	0.016	208.185.188.1	core1.lhr.above.net
7	3/3	0.013	0.015	0.016	208.185.156.14	core2-core1-oc48.lhr.above.net
8	2/3	0.082	0.086	0.091	216.200.127.69	iad-lhr-stm4-2.iad.above.net
9	3/3	0.088	0.097	0.112	209.249.203.230	pop1-vie-p2-0.atdn.net
10	3/3	0.080	0.086	0.089	204.148.99.197	bb1-vie-p6-1.atdn.net
11	3/3	0.093	0.099	0.108	204.148.98.9	bb1-dtc-p5-0.atdn.net
12	3/3	0.089	0.094	0.097	204.148.98.106	pop1-dtc-p14-0.atdn.net
13	2/3	0.088	0.101	0.115	204.148.103.2	ptne1-dc3-p0-0.atdn.net
14	3/3	0.082	0.110	0.141	205.188.240.210	ptni2-dc3-p0-0.ptn.aol.com

Note that the machine performing the test is not displayed.

Hop

-- Gives the order in which the TCP/IP packets progress from machine to machine, called the 'distance' (in hops) from the originating machine.

Result

-- Received/Sent packets, or other information (see below). Assuming all is well, these numbers should match - if more packets are sent than received, there may be a problem.

Min, Avg, & Max

-- The Minimum, Average and Maximum round trip time in seconds that the packets took to go to and return from that machine.

IP & Name

-- The IP address and domain name of the remote machine which is conveying your TCP/IP packets. There are other possible values which can appear in the Result column, identifying network problems with the trace:

!Host, !Network, !Protocol, !Port

-- A Host, Network, Protocol or Port is unreachable.

!Frag

-- Source route failed or fragmentation needed. OT always sets the "don't fragment" bit, so you may get this with some routers that cannot handle the fragmentation bit, even if the packet is small enough that it does not need to be fragmented.

!Route

-- Source route failed.

?Network, ?Host

-- Destination network or host unknown. This is a router error.

Isolated

-- Source host isolated.

XNetwork

-- Communication with destination network administratively prohibited.

XHost

-- Communication with destination host administratively prohibited.

TOS Net

-- Network unreachable for type of service. TOS Host Host unreachable for type of service.

!TTL

-- TTL was very small on the return packet (<=1) so it may indicate that the TTL was incorrectly set on the returning packet. (For a discussion of TTLs, see the section below - How Trace Route Works: TTLs.)

If you double-click a line in a Trace Route window, Interarchy will test that machine with ICMP pings.