Basic Network Troubleshooting

If your computer is unable to connect to a network or browse other computers on the network, there should be a problem with your network.Following may be the reasons

1. The cables are unplugged, or in the wrong port(s)
2. Network card not connected properly.
3. Bad network card drivers or software settings.
4. Firewall preventing computers from seeing each other.
5. Connection related issues.
6. Bad network hardware.

Some General Information
LED is 'ON' doesn't mean that you are connected , It indicates there is power in the cable.
Try the following steps

* Make sure that the cable is plugged well, and into the right port(s)
* Test with a NEW (or another) Ethernet cable (CAT5 or RJ45).
* Unplug your modem and router for a while, and plug them back
* ping -l 1440 -t yahoo.com and wait for the response ( this is for a test only, whether yahoo is pinging or not)
* if you get any dropped packets.stop the pinging. (hit 'Ctrl+C to stop)
* try 216.109.112.135, the IP address of Yahoo.com.
* If you can't ping using yahoo.com, but can ping it using the IP address, most probably is because of the Static Gateway setup
* if network card is new then check that card's resources are properly set and ensure that its is not conflicting with any other resources.
* Verify that the correct protocols are installed on the computer.(Eg TCP/IP, IPX/SPX or NetBEUI)
o Open Network properties by double-clicking "Network connections" in Control Panel.
o Open "Local Area Connection".
o Click the Properties button.
o If the protocol is installed, the protocol should be listed by the installed network adapter.
+ If you wish to re-install the protocol, select the protocol and click the uninstall button
+ Reboot the computer and then continue with the below step
o If the protocol is not listed, click the Add or Install button.
o Select the protocol and click ok.
o Reboot the computer.

* If your network using a firewall, ensure all the required port(s) are open.
disconnect the computer from the firewall to ensure whether firewall is blocking the network.
* Wait for an additional time so that the computer to detect the network
* Try to ping a computer within the LAN
* If you are not loosing any packets , It is evident that the computer is communicating.
* If you still unable to connector browse, there are some another reasons present.
*

Use tracert /traceroute for tracing the route of the packets
o Syntax For Trace the route
+ tracert IP( Eg : tracert ***.***.***.***)

or
+

traceroute IP ( Eg : traceroute ***.***.***.***)

Thanks and Regards
http://webpots.blogspot.com/
Teji Thomas