Everyone working in the IT field has at some point overlooked the obvious or simplest solution to a problem for a more sophisticated explanation at least once in their career. This of course is not intended, but it happens to the best of us. Using a checklist when troubleshooting common issues help us remember to start with the easy and common possibilities before looking into more complicated resolutions. Attached is a network connectivity checklist that can be used by anyone working in IT to help them methodically approach this issue. Another benefit to using a checklist is that it helps document network issues. If necessary, this documentation can be used later to help advocate for a better Internet connection or new equipment. One last benefit to using a checklist is that issues can more frequently be resolved by staff before involving the system administrators or network engineers saving everyone invaluable time.
The steps listed below are those listed in the checklist plus explanations of each.
Verify more than one website domain is not responding
If a user reports they cannot access a single website, it is imperative to try other website domains as well. A single website being unavailable can mean it is down, or is being blocked by a content filter or firewall. Try additional website domains, not other pages on the same website, to see if the issue is only with the one website, or if further troubleshooting needs to be done.
Can local resources be reached?
When a user cannot access the Internet, they often report "everything is down" or "nothing works". Often times though, what is simply an Internet issue is relayed as a complete network breakdown. Before trying anything too serious, verify whether or not the device can access local network resources. If you have an email server onsite, open the email application and see if email will update. Or, try opening local file shares to see if local network resources are accessible. This narrows the issue to being related only to the Internet, or all network resources on that device.
If on a wireless device, try a wired device
If the device that reported the issue connects to the network wirelessly, try accessing the websites using a wired device. This can help narrow the issue to a problem with the wireless network if wired devices work fine while wireless devices do not.
If on a wireless device, check to be sure wireless was not physically turned off
Many wireless devices have keyboard hot keys to turn the wireless off and on. If this button is accidentally pressed, the wireless will will stop working. Going into the network settings and turning a wireless device off and on will normally not fix this issue as these are two different controls for the wireless device. Press the hot key button again to turn the wireless back on. Other manufacturers have physical sliding buttons on the sides or front of laptop cases to turn the wireless off and on. These buttons are often moved on accident by users when moving their laptops. Slide the button back to the on position to turn the wireless back on.
If on a wired device, check the network cable
If the user is on a wired device, verify one end of the cable is plugged into the computer network jack and the other end into a valid network wall jack that is turned on in your MDF / IDF. If no other users appear to be affected, try using a different network cable. If this does not work, verify the corresponding port in your MDF / IDF is plugged into the network stack and that all lights appear to be passing traffic. If other ports are available in your network stack, try moving that cable to a new port to see if the port is bad.
Try a different web browser
If you have multiple website domains that will not open on a single device, try opening the websites on another web browser if one is available. This will rule out the browser which could be compromised or hijacked.
Verify the device has a valid IP address
From a dos prompt, type "ipconfig /all" and press enter. Verify the IP address assigned to the machine is a valid address for your network. If the IP address is not valid, try rebooting the machine. If the IP address is still not valid after rebooting, check the DHCP server to verify it is running correctly and has not run out of IP address leases. If static IP addresses are used, verify the static IP address settings and modify as necessary.
Ping an external website IP address
From a dos prompt, try pinging the IP address of an external website you know responds to ping requests. If reply responses are received, try pinging an external website URL to check to see if DNS is working properly.
Ping an external website URL
From a dos prompt, try pinging an external website URL that you know responds to ping requests. If you receive replies from the IP address ping request but not the website URL ping, then the issue is with DNS. Verify your DNS server, whether hosted internally or externally, is running correctly. Also, verify the DNS settings on the local computer match what the network DNS settings should be. To check the DNS settings on the local computer, use the "ipconfig /all" command in the dos prompt.
Try a different device
In an event nothing else pans out, try accessing website domains from another device located at the same site using the same user credentials if possible. Using the same credentials takes content filter rules out of the equation as these are often applied uniquely to different users. If other devices are able to access the website domains, then the problem on the device with the issue could be the any of the following:
- Wireless or wired NIC was turned off in the software
- Wireless NIC has physically stopped working
- Wired NIC has physically stopped working
- Cabling in the walls to the network jack the wired device is plugged into is bad (rare)
- Port in the network stack the network jack corresponds with has physically stopped working
- Cable in the network stack that corresponds to the network jack has been unplugged