Diagnosing Network Issues Part 1

Problem 1:

All users on a small LAN are unable to connect to the internet but are able to connect to the home group and shared resources such as the wireless printer.  There are 4 PCs that are wired directly to the router, 3 laptops and 4 tablets, with the exception of 2 of the tablets, the rest of the machines are all running Windows 10 Professional.

Scope:

In this case of this scenario all users are affected (11 users). 

Troubleshooting

The fastest way according to the article to determine who is effected would be to do a local test of your own machine by doing a reboot of your PC, modem and router, and at least one other device connecting to the network, preferably a wireless on if your first device is wired, this helps kill two birds with one stone.  In a small office environment like ours we usually reboot only our PC or laptop first and while that is going on ask our team verbally if they are also seeing an issue BEFORE we bump the router and the modem so we don’t knock anyone off the internet who may be tunneling out to a client site and would have their work disrupted by an unannounced restart.  Once the above scenario was established, we would check the modem and router.  Normally you can check to see if everything is up by the lights on the modem and router but not all routers will have lights and sometimes those lights malfunction, so we would power cycle both.  We also usually power cycle one at a time.  So, we do this and still no internet, modem lights appear to be in order.  The article speaks to checking connections first, and before cell phones could connect to the internet that would be the next logical step, but we would check our ISP site quickly via our phone before pulling cables.  Now, because we have established everyone on the LAN cannot connect to the internet and our quick check of the ISP site indicates no outages, we want to take a closer look at the router.  Now on our office router we notice none of the connection lights for the wired ports are lit and wireless connection light is not lit either, on this particular router there is a light for internet and it is a solid amber which means the connection is down.  But wait, the modem lights are indicating it is connected and the ISP site say everything is fine!  So we either have a bad cable or the router has a problem.  We swap out the Ethernet cable between the modem and router.  Luckily this returns the LED for internet access back to the expected white, and we don’t have to look at replacing the router.   Another check on the router if we didn’t have the lights or we knew we had faulty lights could have been to check our IP access using ipconfig and checking to see if it was returning the correct range of IP address.