Cisco

Ping: Request timed out vs. Destination Host unreachable

Often executed – often not well interpreted. What is Ping? Ping is the network troubleshooting tool No. 1. Ping sends ICMP packets to an IP device. In the expection, that the remote device will respond with an ICMP Echo Reply. But what does the error request timed out mean? And what means destination host unreachable?

In the following screenshot, ping was successful.

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192.168.0.2 responds to the 32-bytes packet in 1 ms and the TTL value is 128 (number of maximum hops). Everything ok so far, the device is up and responding with an ICMP Echo Reply.

Request timed out

So, now it becomes more interesting: A computer with the IP-Address 192.168.0.2/24 is not responding. My IP-Address is 192.168.0.1/24. Therefore both devices are on the same subnet and in the same broadcast domain.

Unbenannt

What can we learn from it?

Request timed out (local subnet) means, that the device does not send ICMP packets in a certain amount of time. Nothing else. The “Request timed out” error cannot be used to indicate anything other than the fact that the device is not responding to ICMP packets. In most cases, unlike ping, the ARP Request was successful. Host 192.168.0.2 is up!

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Most likely, Windows Firewall is causing the problem:

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After activating “Echo Request – ICMPv4-In”, the device starts sending ICMP Echo Replys.

Destination host unreachable

This brings me to the next error message. While trying to do a ping to a host in my subnet, I get Destination host unreachble.

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What can we infer from this? This situation is more complex and there may be several reasons. The computer could be switched off. For checking, run arp -a to find out whether the computer responds to arp requests. In most cases the ARP request has failed as well.

arp -a

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See also

If you get the error “Transmit failed General Error”, see my article Ping: Transmit failed. General failure.

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