TCP/IP for Beginners - Troubleshooting TCP/IP & IP Addresses on Networks

Troubleshooting TCP/IP can be a nightmare if you are unfamiliar with basic TCP/IP addressing. Be sure to read the complete series if you are unfamiliar with the addressing of TCP/IP because we examine the commands and tools used to correct TCP/IP errors throughout this series.

Basic troubleshooting usually occurs when you can't get on the internet, use a shared folder, or you can't print to a shared printer.

Your computer's TCP/IP is bound (software to hardware). This means that commands and programs using the internet use the software to talk with the hardware. In order to perform basic test, ping your own IP address.

1. Start
2. Run
3. CMD
4. Ping 127.0.0.1

Go to a command prompt and type tracert www.brighthub.com . You should get returns at every stage of the communication process. Where the request drops, is where the problem is. Here is an example of tracert:

Tracing route to www.brighthub.com [66.165.142.74]

over a maximum of 30 hops:

1 803 ms 147 ms 193 ms 132.sub-66-174-175.myvzw.com [66.174.175.132]

2 134 ms 147 ms 243 ms 66.174.175.255

3 125 ms 193 ms 150 ms 194.sub-69-83-61.myvzw.com [69.83.61.194]

4 191 ms 162 ms 146 ms 229.sub-69-83-60.myvzw.com [69.83.60.229]

5 146 ms 158 ms 181 ms 194.sub-69-83-60.myvzw.com [69.83.60.194]

6 159 ms 159 ms 158 ms 26.sub-69-83-60.myvzw.com [69.83.60.26]

7 163 ms 163 ms 145 ms 9.sub-69-83-60.myvzw.com [69.83.60.9]

8 169 ms 188 ms 149 ms 13.sub-69-83-48.myvzw.com [69.83.48.13]

9 243 ms 295 ms 181 ms 170.sub-66-174-38.myvzw.com [66.174.38.170]

10 225 ms 170 ms 159 ms 253.sub-69-83-32.myvzw.com [69.83.32.253]

11 168 ms 289 ms 178 ms GigabitEthernet1-0.GW2.GSO1.ALTER.NET [157.130.89.133]

12 220 ms 189 ms 327 ms 0.so-4-0-1.XL1.GSO1.ALTER.NET [152.63.36.146]

13 346 ms 333 ms 857 ms 0.so-6-0-0.XL3.IAD8.ALTER.NET [152.63.0.138]

14 259 ms 206 ms 250 ms 0.ge-6-1-0.BR2.IAD8.ALTER.NET [152.63.41.153]

15 223 ms 726 ms 239 ms te-11-2-0.edge1.Washington4.level3.net [4.68.63.165]

16 321 ms 312 ms 388 ms vlan69.csw1.Washington1.Level3.net [4.68.17.62]

17 217 ms 194 ms 289 ms ae-64-64.ebr4.Washington1.Level3.net [4.69.134.177]

18 217 ms 195 ms 238 ms ae-3-3.ebr1.NewYork1.Level3.net [4.69.132.94]

19 227 ms 279 ms 387 ms ae-61-61.csw1.NewYork1.Level3.net [4.69.134.66]

20 188 ms 234 ms 304 ms ge-7-0.ipcolo2.NewYork1.Level3.net [4.68.97.14]

21 224 ms 185 ms 180 ms WILTEL-INTE.ipcolo2.NewYork1.Level3.net [4.78.191.54]

22 175 ms 289 ms 282 ms 69.89.236.98

23 315 ms 179 ms 180 ms 66.165.142.74

Trace complete.

If you can't get on the internet follow these steps to attempt to correct your problems.

1. Unplug your broadband modem and wait 30 seconds
   • This resets your modem and should correct any problems with TCP/IP
   • You should get a LAN light and a DSL or Ready light
2. Unplug your router and wait 30 seconds.
   • This should reset the router and correct any problems
3. Reboot your computer.

With all three devices reset, this should reset any problems you have.

If you don't have an IP address:

1. Check your LAN connection. The cable should be plugged into both the router and your computer. You should have a LAN light (link light) on your router.
2. Check your IP address
   • Go to Start
   • Click on Run and type CMD
   • Type IPConfig
     • If you do not have an IP address:
       • type IPConfig /release
       • type IPConfig /renew This should give you an IP address of one of the private ip address
3. If you continue to have problems, try the following utility:
   • Winsock Fix Link
   • Use Netsh (See Advanced Troubleshooting Below)
4. Check your devices under System Information / Device Manager
   • If the driver is missing, obtain and install the driver
5. Go to a CMD prompt and type IPConfig /flushdns

First you can test your network bindings by using the GUI (graphic user interface) program:

* netsh diag gui (Windows XP)

To repair and reset the winsock in Windows Vista:

1. Click on Start

2. Type Cmd

3. Press Ctrl-Shift-Enter keyboard shortcut to run this as the Administrator.

4. Type netsh winsock reset - press the Enter key.

5. Restart the computer.

Reinstalling the TCP/IP protocol in Vista can often correct issues that cannot be resolved by the above steps:

1. Click on Start

2. Type Cmd

3. Press Ctrl-Shift-Enter keyboard to run as the Administrator.

4. Type netsh int ip reset - press the Enter key.

5. Restart the computer

This method should be used when all else fails.

You should reset at your own discretion. Resetting your Winsock should only follow the resetting of your router / modem and computer.

How to break down IP addresses into Networks and Host (computers and devices) follows in the next part of this series.