Ref: https://tnind.wordpress.com/basic-network-connectivity-troubleshooting/

UNABLE TO CONNECT TO NETWORK COMPUTER ON LAN

TROUBLESHOOTING NETWORK CONNECTIVITY IN AN IP NETWORK:

One of the most common issues that come up, both, as a Computer User and a Technician, is that of Network Connectivity. You might suddenly not be able to access / logon to a server or another computer.

Follow the following steps given below, in that order, to troubleshoot and fix this issue.

1. Check the IP address of the user’s computer – is it getting an IP address or not? Or is it getting an APIPA IP address – like 169.254.xxx.xxx? Use the ipconfig /release and/or ipconfig /renew commands and check if the computer gets a valid IP address.

2. Restart the computer and check again – does it work now?

3. Ping the loopback (diagnostic) IP address, 127.0.0.1: If the ping is successul, then, the TCP/IP stack is good. If the ping was not successful, then, you will have to reinstall the TCP/IP stack in the users computer.

4. Ping the User’s Computer: If you get a successful PING, it means that the user’s NIC is working well.It also means that the TCP/IP in the User’s computer can communicate with the NIC in the same computer.

If the Ping is not successful, it could be a problem with the NIC in the User’s computer.

5. Ping the Default Gateway (The Router):If the PING is successful, it means that the NIC can communicate with the LAN and that the physical cable connnections to it are okay. If this PING fails, then it could mean a problem with the physical connections which could be anywhere between the NIC and the Router.

6. Ping the Remote Server (or the computer the User is not able to logon to): If you are able to ping the remote server but still not able to logon, it could be a problem with the DNS settings. But if the PING fails, it could mean a problem with a physical connection and you will need to manually check the connections from the PC to the Server.

Some important definitions:

Ping: It stands for Packet InterNet Gopher. (Gopher = Status). For more help on PING open a command windows in your computer and type in PING/? and check the options.

Tracert: It is a command used to display the number of routers on the path to the destination host. You can get more on the Tracert command by typing tracert/? in a command window in your computer.

IPConfig: It shows you the IP address configuration of your computer on a network. (It also shows you your computer’s IP address on a network.)