Evan Schapiro
You can learn a lot about how TCP/IP works by trying out some commands typically used by system administrators to diagnose problems and/or to see if configurations are working properly.
This exercise focuses on IP addressing and routing by using the following commands:
ipconfig
tracert
There is no standard user interface to these commands, they must be run from the command shell. (This was the standard interface for MS-DOS computers before Windows). The best way to open a command shell is to choose “Command Prompt” (MS-DOS Prompt in Windows 98 or below) from the Start/Programs menu. You can also choose Start/Run and type the command directly into the text box.
Try these commands from different computers (e.g. home, work, school) and compare the results. See if you can figure out what’s different and why.
This command details how IP is setup on the machine you are logged into.
At the command prompt, type: ipconfig
Your result should be something like this:
IP Address. . . . . . . . . : 208.192.102.196
Subnet Mask . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . : 208.192.102.1
For more detail, type: ipconfig /all
If the info scrolls off the screen, you can type: ipconfig /all | more
(Hit enter to scroll to the next screen).
Your result should be something like this:
Windows NT IP Configuration
Host Name . . . . . . . . . : 3VEXP
DNS Servers . . . . . . . . : 199.172.62.5
199.172.62.20
Node Type . . . . . . . . . : Broadcast
NetBIOS Scope ID. . . . . . :
IP Routing Enabled. . . . . : No
WINS Proxy Enabled. . . . . : No
NetBIOS Resolution Uses DNS : No
0 Ethernet adapter :
Description . . . . . . . . : PPP Adapter.
Physical Address. . . . . . : 44-45-53-54-00-00
DHCP Enabled. . . . . . . . : Yes
IP Address. . . . . . . . . : 208.192.102.196
Subnet Mask . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . : 208.192.102.196
DHCP Server . . . . . . . . : 255.255.255.255
Primary WINS Server . . . . :
Secondary WINS Server . . . :
Lease Obtained. . . . . . . : 01 01 80 12:00:00 AM
Lease Expires . . . . . . . : 01 01 80 12:00:00 AM
For a list of command line options try: ipconfig /h
This command shows you all the routers that your TCP/IP message goes through in order to make a connection to another IP address.
At the command prompt, type: tracert xxx
Where xxx is the IP address or URL of the machine that you are trying to connect to.
e.g. tracert brandeis.edu
Here is the result of tracert from my home computer to brandeis.edu.
Notice that DNS has resolved the name “brandeis.edu” to 129.64.99.33
Tracing route to brandeis.edu [129.64.99.33]
over a maximum of 30 hops:
1 158 ms 139 ms 139 ms fxtc2-c.std.com [199.172.62.221]
2 135 ms 150 ms 149 ms Boston-STD-F.std.com [199.172.62.80]
3 166 ms 145 ms 134 ms Loopback0.GW5.BOS1.ALTER.NET [137.39.4.111]
4 131 ms 159 ms 149 ms 153.ATM3-0.XR1.BOS1.ALTER.NET [146.188.179.242]
5 227 ms 209 ms 169 ms 191.ATM10-0-0.BR1.BOS1.ALTER.NET [146.188.177.1]
6 163 ms 149 ms 149 ms 137.39.23.90
7 145 ms 159 ms 139 ms p1-0.bstnma1-ba1.bbnplanet.net [4.24.4.193]
8 147 ms 140 ms 150 ms p2-3.cambridge1-nbr2.bbnplanet.net [4.0.2.173]
9 180 ms 151 ms 184 ms p0-0-0.cambridge1-cr21.bbnplanet.net [4.0.1.210]
10 170 ms 141 ms 170 ms s0.brandeis2.bbnplanet.net [4.1.136.6]
11 168 ms 209 ms 170 ms gw.border.brandeis.edu [129.64.254.1]
12 175 ms 179 ms 190 ms brandeis.edu [129.64.99.33]