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The ping command is a widely used and supported network troubleshooting utility.

It can be found on pretty much any operating system, from Windows, Mac and Linux, to even switches, routers and firewalls.

Ping uses ICMP, or the Internet Control Message Protocol, to test connectivity between two nodes.

The name ping comes from sonar. Sonar works by sending out sound waves and detecting any echoes reflected back by objects. Ping works in a similar way.

By sending a receiving a successful ping, you can determine if a system is on the network, and most importantly, if you can reach it.

There will be times when some, or none of the replies come back, and there are a few things that could cause this.

Request Timed Out
Then the most obvious cause of this error is that the system you’re trying to reach doesn’t exist, isn’t powered on, or isn’t connected to the network.

Another reason why a system might not respond to a ping is due to the firewall.

Destination Host Unreachable
This error generally indicates that a route to the destination cannot be found. This could be from the localhost or the default gateway.

Ping could not find the host
This means your computer was unable to resolve the hostname to an IP address indicating a potential DNS server issue.

That's what happened when you have complete packet loss. Where things can get a bit more difficult to troubleshoot is when you only get partial packet loss, meaning some pings get replies but others don’t.

This can be caused by any number of things but generally, it means something is not behaving the way it should

Some examples are
Broken network cards
Broken cables
Problems with the switches or routers

And this could be at any point between you and the machine you are trying to reach.

So for that reason, complete packet loss is usually easier to troubleshoot.