Troubleshoot offline network

This article is a WIP.

Identify the problem

Start at the modem/ONT. Take note of the lights that are on and the color of the lights.
Do the same for the router.
If you don't immediately identify the issue (modem or router offline), proceed to a computer.
Do an ipconfig on Windows or ifconfig on Mac/Linux. Do you have an IP and a gateway?
Ping the gateway. ping <gateway-ip> -t on Windows and ping <gateway-ip> on Mac. Fill in the <gateway-ip> with the actual gateway IP retrieved from the ipconfig command.
Also ping out to the internet. 1.1.1.1 and 8.8.8.8 are reliable public IP addresses to ping.
Also ping out to a domain, such as google.com.
Identify where the connection is failing.
1. If you can't ping the gateway, it is not an internet problem - it's a local issue caused either by your computer, the switch(es) in between you and the router, or the router (or, less likely, an ethernet cable).
2. If you can ping the gateway but can't ping 1.1.1.1 or 8.8.8.8 then it is an internet issue, which typically is out of our control. There is a chance that it could be the router, still. See below
3. If you can ping the gateway and the public IP Addresses above, but can't ping google.com, then there is a DNS issue.
4. If you can ping everything above, then the issue may be in connection reliability. Let the pings run for a few minutes, and monitor the average response time and look for timeouts or dropped pings. After a few minutes, you can press CTRL+C to stop the ping test and get a summary view.
  1. Pings to the router and other local devices should generally be <1ms for wired connections and <10-30ms for wireless connections.
  2. Pings to the internet should be 30-60ms for cable and fiber internet services. DSL and Satellite internet services may be significantly slower and have packet loss, but this is not necessarily indication of an immediate issue (this could just be the normal state of those internet connections).