BASIC NETWORK DEBUGGING 1

BASIC NETWORK DEBUGGING

1) TCPIP Protocol. Open a DOS window and ping 127.0.0.1. This is the automatically created local machine IP address. You should see something like:

C:\>ping 127.0.0.1

Pinging 127.0.0.1 with 32 bytes of data:

Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128

Ping statistics for 127.0.0.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

For a failure you'll usually get a response like:

Request timed out.
Request timed out.
Request timed out.
Request timed out.

OK? Go to #2.
FAIL? Your TCPIP protocol is not working. Contact Microsoft for help. A good document they provide is:

http://support.microsoft.com/kb/314067/ (PDF)

Note that under Windows XP it is not possible to re-install TCPIP like you could under earlier Windows versions. Microsoft considers TCPIP a core Windows component now. It is still possible, however, for the TCPIP protocol stack to before corrupted. Microsoft documents a technique that can be used with Windows XP SP2 to reset the TCPIP protocol and often recover from this problem. See:

http://support.microsoft.com/default.aspx?scid=kb;en-us;299357 (PDF)

It's also possible that the problem is in the Windows WINSOCK portion of the network stack. Microsoft provides information on diagnosing these issues as well:

http://support.microsoft.com/kb/811259/ (PDF)

2) TCPIP Protocol. Open a DOS window and ping your machine's IP. If you don't know your IP, open a CMD window and type IPCONFIG. This should provide you with the IP assigned to your adapter. If you don't get an IP return to step #1. An adapter must have an IP address to function properly. Are you using DHCP (i.e Obtain IP Address Automatically) or are you using a static IP address? If DHCP, is your DHCP server working? If static, is it a valid static IP address for your network? Don't know these answers? Ask your network administrator or ISP for assistance.

OK? Go to #3.
FAIL? Your TCPIP protocol is not setup properly. Check with your network
provider and or Microsoft for help.

3) TCPIP Protocol. Open a DOS window and ping your default gateway. If you don't know your default gateway get it with the IPCONFIG command as in step #2. The default gateway is the IP address where Windows will send all traffic that is destined for the internet. If the default gateway is not set, set wrong, or unreachable, you will not have internet access.

OK? Go to #4.
FAIL? Your network is not working or your gateway is down. Check with your
network administrator.

4) TCPIP Protocol. Open a DOS window and ping your DNS server(s). If you don't know your DNS server addresses, use the IPCONFIG command with the /ALL switch will report them. If the DNS servers are not set, set incorrectly, or unreachable you may have internet connectivity but will not be able to access internet sites by name. This makes internet use almost impossible.

OK? Go to #5.
FAIL? Your DNS server is wrong or is not working. Check with your
network administrator.

5) Name Resolution. Open a DOS window and ping your machine by name. Don't know your machine name? Get it from the My Computer>Properties and the Computer Name tab. Look for the "Full computer name" field.

OK? Go to #6
FAIL? Your DNS resolution is not working. Have your DNS administrator or
network service provider check that your machine is actually in the
DNS database.

6a) Name Resolution. Open a DOS window and try "NSLOOKUP www.netswitcher.com" (NT/2000 only) This tests to see if the DNS server and the name resolution of your machine is working properly for internet hostnames.

OK? Go to #6b.
FAIL? Your DNS server or your internet connection is not working properly.
Have your DNS administrator check your DNS server and/or your network
provider check your internet connection.

6b) Name Resolution. Open a DOS window and try "ping www.netswitcher.com" (Win9x/ME)

OK? Go to #7.
FAIL? Your internet connection is not working. Have your network administrator
check your network and/or contact your internet service provider.

7) TCPIP Apps. Open a DOS window and try to telnet to a web server on port 80. (i.e. "telnet www.netswitcher.com 80") Do you get a connection or a failure?

OK? Go to #8?
FAIL? Are you behind a proxy or firewall? Is this a permitted or supported operation?
Do you need to connect through a proxy? Contact your network administrator or
internet service provider for assistance.

8) Application proxies. Check your IE properties. Are you setup to use a proxy? Do you NEED to use a proxy? Be sure the setting matches your required configuration.

OK? Go to #9
FAIL? Perhaps your proxy doesn't support this application. Check with your network administrator
or internet service provider.

9) Application. Can you open a web page by name? Try http://www.netswitcher.com

OK? All is well.
FAIL? Perhaps www.netswitcher.com is down. Try some other sites. http://www.microsoft.com or another well known site.

This page was last updated on 08/04/2006. If you have any suggestions or corrections, please contact joe @ netswitcher.com.