Everything about network diagnostic tools

Windows XP and Windows Vista includes many tools that will allow you to test your LAN and your Internet connection to detect problems. The command used to diagnose network problems is the ping command. It can test the connectivity of a remote computer by sending packets of data.

The tracert command in turn determines the route leading to a destination. You can find every piece of equipment that sits between your computer and the destination you specify.

The ipconfig command will display the values of the current configuration of your TCP / IP, and update their parameters by DHCP and DNS.

Finally, in addition to these commands, other tools are included in Windows to help you better understand your network environment and give you leads in solving your problems: ARP, netsh, netstat, net ...

Ping:

The command used to diagnose network problems is the ping command. It can test the connectivity of a remote computer by sending ICMP echo packets. If the computer responds to ping, is that it is reachable and, therefore, that your network has no problems physically.

Thus to check that your LAN is set up, you simply "ping" each computer and see if they respond.

Suppose you have two PC network, a first IP address 192.168.1.12 and a second IP address 192.168.1.108.

1. To test the network connection between two PCs, go on the first PC, then click the Start button and then click Run.
   
2. Enter cmd, and then confirm by pressing Enter.
   
3. A command prompt window opens. Then enter the following command: ping 192.168.1.108 and press the Enter key.
   
4. Your computer will then send a series of packets to the IP address 192.168.1.108. If these packages arrive its destination, you get a response from the remote computer. The time it takes for packets to get back to you is also indicated, this is called latency.
   
5. If, however, these packages are not the addressee, which means a misconfigured network, you get the message "host unreachable destination" or "Timeout exceeded demand. In this case, check your network configuration.
   
6. To verify that the Internet is functional, you can perform a ping on a network server, such as the Google search engine. Now enter the command ping www.google.com, then confirm with Enter. Note the absence of the prefix http://.

In case of failure, also test the IP address of a server Google pinging 209.85.135.109. If you are still unable to reach the destination host is your Internet connection is not active.

The tracert command:

The tracert command determines the route leading to a destination by sending ICMP echo messages (in the same way as the ping command). Each piece of equipment that sits between your computer and the destination that you specify is then displayed. This command is useful for identifying a problem on an intermediate router (eg your box).

1. Open a command prompt by clicking Start then Run.
   
2. Type cmd and press Enter by.
   
3. Then enter the following command: tracert 209.85.135.109. Confirm with Enter.
   
4. Your computer will then determine the route to reach the address 209.85.135.109 (a Google server).
   
5. If you connect to the Internet through a router or a PC whose connection was shared (by the PC then acts as a router), the interruption of the connection to the router means that the latter 's is not connected to the Internet. So check its parameters and connections.
   
6. If you can not reach the destination host and no route is displayed, your router is not recognized. Verify connectivity using the ping command. If it responds normally, is that you have not set a gateway on the PCs that connect to the Internet through the router.

Ipconfig:

The ipconfig command displays the values of the current configuration of your TCP / IP, and update their parameters by DHCP and DNS.

1. Open a command prompt by clicking the Start button and click Run.
   
2. In the Run dialog box, type cmd, and then confirm with Enter.

View the TCP / IP based network adapters all:

1. To view the TCP / IP based network adapters all, that is to say only the IP address, subnet mask and the values of the default gateway of each card, enter the following command : Ipconfig.
   
2. Then confirm with Enter. The TCP / IP on your computer is displayed.
   
3. To view the TCP / IP complete all network adapters, use the / all parameter with the ipconfig command: ipconfig / all.
   
4. You will have information on the physical address (also called MAC address) of your network cards, the DNS servers used, the name of your computer, and other more or less useful.

Renewing the TCP / IP:

If your TCP / IP is obtained dynamically via a DHCP server, you can renew, and then update it using the parameter / renew.

1. In a Command Prompt window, type the command ipconfig / renew.
   
2. Then confirm with Enter. The TCP / IP is updated.

Clear the DNS resolver cache:

If you access a website only by IP address instead of its domain is most likely due to a change DNS settings on the remote server. Such information may take a few days before arriving at your PC.

• To flush the DNS resolver cache and reset its contents, type the following command: ipconfig / flushdns.
  
• Confirm the command by pressing the Enter key. The DNS information will then be updated.

Some other useful commands:

In addition to ping, tracert and ipconfig, other tools are included in Windows to help you better understand your network environment and give you leads in solving your problems.

Here is a list of useful commands that you will probably need one day or another.

1. arp-a: Displays the MAC address translation table, IP address.
   
2. Netsh: Utility to view and modify the configuration of network layers. Enter?, Then confirm by pressing Enter each time to view the list of available commands.
   
3. netstat-rn: Displays the routing table TCP / IP.
   
4. netstat-an: Displays a list of all TCP / IP sockets used for all clients and all servers.
   
5. net share: Displays a list of all the partitions, files as printers, available on the machine.