When I ping an IP address, what is the difference between Request timed out and Destination host unreachable returned from the command?
This question is related to
networking
ping
icmp
As khaos said, a destination unreachable could also mean that something is blocking the way from or to your destination. For example an ACL that filters bad IP addresses.
Put very simply, request timeout means there was no response whereas destination unreachable may mean the address specified does not exist i.e. you typed in the wrong IP address.
Request timed out means that the local host did not receive a response from the destination host, but it was able to reach it. Destination host unreachable means that there was no valid route to the requested host.
As I understand it, "request timeout" means the ICMP packet reached from one host to the other host but the reply could not reach the requesting host. There may be more packet loss or some physical issue. "destination host unreachable" means there is no proper route defined between two hosts.
Source: Stackoverflow.com