When a network is working, all is well. But what happens when it quits working? If a user calls in saying they can't access a particular server or webpage, we need a way to see if it is a local problem or a problem with the network. Here are several tools you can use to figure this out.
Ping
Ping is a command-line utility which will send a packet to a remote host, and if the host recieves the message then it will echo the packet back. This can be used to test a connection to a certain host. Ping uses the ICMP (Internet Control Message Protocol, RFC 792) Ping is avaliable standard on most operating systems, including Win95/98/NT, and all flavors of UNIX
usage: ping host [optional switches]
$ ping falcon.jmu.edu
PING falcon.jmu.edu (134.126.10.30): 56 data bytes
64 bytes from 134.126.10.30: icmp_seq=0 ttl=240 time=208.4 ms
64 bytes from 134.126.10.30: icmp_seq=1 ttl=240 time=180.2 ms
64 bytes from 134.126.10.30: icmp_seq=2 ttl=240 time=170.1 ms
64 bytes from 134.126.10.30: icmp_seq=3 ttl=240 time=161.3 ms
64 bytes from 134.126.10.30: icmp_seq=4 ttl=240 time=159.0 ms
64 bytes from 134.126.10.30: icmp_seq=5 ttl=240 time=152.5 ms
--- falcon.jmu.edu ping statistics ---
6 packets transmitted, 6 packets received, 0% packet loss
round-trip min/avg/max = 152.5/171.9/208.4 ms
Traceroute
Traceroute is a utility which can be used to monitor the route a packet takes from source to destination. It can be used to pinpoint where problem lie in the routing between the source host and the destination. The traceroute command is avaliable standard with Windows9x/NT operating systems, and also with all flavors of UNIX. On Windows platforms, the command is "tracert", while on UNIX it is "traceroute".
usage: traceroute host [optional switches]
$ traceroute falcon.jmu.edu
traceroute to falcon.jmu.edu (134.126.10.30), 30 hops max, 40 byte packets
1 tnt1.man.va.rcn.net (10.65.17.11) 118.371 ms 105.539 ms 119.569 ms
2 fe1-0.core1.man.va.rcn.net (10.65.17.1) 109.460 ms 99.351 ms 99.579 ms
3 s0-1-0.core7.spg.va.rcn.net (10.2.3.46) 99.590 ms 109.459 ms 109.669 ms
4 fe0-0-0.core1.spg.va.rcn.net (207.172.0.9) 99.452 ms 99.445 ms
fe4-0-0.cor e2.spg.va.rcn.net (207.172.0.4) 99.607 ms
5 poet0-1-1.core2.tco.va.rcn.net (207.172.9.38) 109.314 ms 119.330 ms
poet2- 1-0.core1.tco.va.rcn.net (207.172.9.42) 109.675 ms
6 fe1-0-0.border2.tco.va.rcn.net (207.172.9.222) 109.245 ms 99.148 ms 111.9 40 ms
7 erols.mcl1.cais.net (209.8.128.13) 127.170 ms 99.374 ms 99.706 ms
8 fe3-1.mcl2.cais.net (209.8.159.42) 119.477 ms 109.288 ms 109.594 ms
9 sl-gw9-dc-9-0-T3.sprintlink.net (144.228.128.5) 129.559 ms 109.250 ms 109 .713 ms
10 sl-bb10-rly-3-0.sprintlink.net (144.232.7.185) 109.573 ms 109.419 ms 109. 591 ms
11 sl-bb6-dc-0-0-0.sprintlink.net (144.232.7.170) 129.464 ms 109.277 ms 109. 580 ms
12 sl-gw1-dc-0-0.sprintlink.net (144.228.20.3) 109.739 ms 109.317 ms 109.629 ms
13 sl-vwan-1-0-0-T3.sprintlink.net (144.228.77.226) 129.545 ms 119.224 ms 11 9.624 ms
14 jmu-router.networkvirginia.net (192.70.138.199) 129.646 ms 129.223 ms 129.583 ms
15 bottom.jmu.edu (134.126.2.6) 129.543 ms 119.370 ms 119.730 ms
16 falcon.jmu.edu (134.126.10.30)
NSLOOKUP
NSLOOKUP is a utility which can be used to query DNS servers for information. For information on NSLOOKUP, please see the page on DNS.
E-mail comments to Lon Jarvis jarvislb@jmu.edu
last updated 3/17/00