If you have ever tried to ping a computer that is offline, you will see one of two responses:
The difference is what is responding:
- If you see REQUEST TIMED OUT, the destination host had no reply within 1 second.
- If you see REPLY FROM XX.XX.XX.XX: DESTINATION HOST UNREACHABLE, the router (network switch) the destination computer is connected to is responding that it has no route to destination computer
Microsoft has a longer explanation you might find helpful:
Request Timed Out
This message indicates that no Echo Reply messages were received within the default time of 1 second. This can be due to many different causes; the most common include network congestion, failure of the ARP request, packet filtering, routing error, or a silent discard. Most often, it means that a route back to the sending host has failed. This might be because the destination host does not know the route back to the sending host, or one of the intermediary routers does not know the route back, or even that the destination host’s default gateway does not know the route back.
Destination Host Unreachable
This message indicates one of two problems: either the local system has no route to the desired destination, or a remote router reports that it has no route to the destination. The two problems can be distinguished by the form of the message. If the message is simply “Destination Host Unreachable,” then there is no route from the local system, and the packets to be sent were never put on the wire. Use the Route utility to check the local routing table.
If you are trying to troubleshoot with PING, you will find these two items helpful: