Network connectivity issues can be complex to troubleshoot.
I will try to list my troubleshoot guide for basic connectivity issues:
1. Physical Connectivity:
Although it is obvious, on most times people only check it last...
go through all your networking gear: from the jack on the wall to the Network RJ45 on your PC.
- Release & reconnect all the cables from the all to the network equipment and your computer.
- if connected to ADSL, make sure you have a Phone-Filter on all your phone-jacks using the same line.
- if you use a modem, check it is Sync'ed (ADSL/Cable Link LED is On & Steady)
- try restarting your Router, Hub/Switch. sometimes there's more then one device forming the network. for
example, a router & a modem on one floor and another switch & Wireless AP on a second floor.
- check to see if you have LED lights on the Network-Card on your PC and on the Network device.
- make sure the network cables are firmly attached and have their safety-latch intact.
2. Resetting your TCP/IP, WinSock & Network Card Settings
Windows uses protocols, drivers & software to operate the network magic. we need to make sure everything is setup correctly and not broken.
- Reset the TCP/IP Protocol:
In Windows XP SP2 and above (Including Vista) we can use this command: netsh int ip reset log.txt
- Reset the WinSock:
In Windows XP SP2 and above (Including Vista) we can use this command: netsh winsock reset
- Tools: On older versions of Windows we can use some tools to help us to the fix: WinsockFix , NetRepair
- Reset the Network Card:
a. Make sure your TCP/IP settings are correct:
Control Panel>Network Connection>Local Area Connection>R-click and Properties>Internet
Protocol TCP/IP Properties > make sure the IP address and DNS settings are set to Automatically or
Manually according to your network setup. if you're not sure you can always write down the current
setup, try the opposite and later undo the changes it's not working.
While you're there, make sure you have all the networking component setup. for most Microsoft-Based
Networks you should see (at least) 3 components:
Client for Microsoft Networks, File and Printer Sharing Service, Internet Protocol TCP/IP
b. Try repairing the connection by: Control Panel>Network Connection>Local Area Connection>r-click
and choose Repair. the Repair process is equal to Releasing & Renewing the IP and clearing the DNS &
ARP cache. you can also to it manually from the CMD is your wish to make it manually:
CMD> ipconfig /release
CMD> ipconfig /renew
CMD> ipconfig /flushdns
c. Try Uninstalling/Reinstalling the network device from Device Manager
(r-click My Computer>Manage) the plug & play process makes it quick and easy and the result is a
network card that resets to defaults settings.
If nothing works...
Try having another PC/Laptop connect to the same cable and see if it works
Try temporarily-disabling and Firewall, Antivirus, VPN/Proxy Software running.
Check your connectivity with different software (maybe the IE is broken but Skype works fine...)
Of course there are many more things to check but these are the most important basics you need to know.
I haven't even written about nothing regarding Ping, Tracert, localhost, host file and many other useful information, but these will probably come in a later post :)