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When I ping an IP address, what is the difference between Request timed out and Destination host unreachable returned from the command?

apaderno
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Suresh Kumar Veluswamy
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5 Answers5

179

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.

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.

If the message is "Reply From < IP address >: Destination Host Unreachable," then the routing problem occurred at a remote router, whose address is indicated by the "< IP address >" field.

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.

For more info Refer: http://technet.microsoft.com/en-us/library/cc940095.aspx

petchirajan
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    So how do you fix this, "If the message is "Reply From < IP address >: Destination Host Unreachable," then the routing problem occurred at a remote router, whose address is indicated by the "< IP address >" field." – Komengem Jun 18 '14 at 16:21
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    What does it mean if you get a mix of both replies? – user2924019 Nov 16 '16 at 15:56
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    What does it mean when you get "Reply From < IP address >: Destination Host Unreachable,", with being the local ip address of the machine you're pinging from (not the gateway or router or ...)? – sanderd17 Feb 03 '17 at 07:11
  • @sanderd17 I have the same issue, did you figure it out? Trying to ping a new Centos 7 install from a Windows machine, I get "Reply From : Destination Host Unreachable" – Matt Feb 20 '17 at 13:38
  • @Matt IIRC, it just means a problem with the DNS. Could still be your router, or the lmhosts config file. The problem isn't necessary with your computer. – sanderd17 Feb 20 '17 at 14:50
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    Thanks @sanderd17, in case anyone else lands here I figured it out: My Linux server was configured with an Ethernet interface with static IP (which I pulled the cable out of once wifi was working) and a Wireless interface that was actually connected. Because of the static IP the Linux server saw the Ethernet inteface as still enabled even though it didn't have a cable any more, and (I think) was trying to reply to my Wireless ping on the Ethernet interface... or something like that. Disabling the Ethernet interface fixed it, anyway! – Matt Feb 20 '17 at 18:31
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    To check if there is no route on the local host to the remote, ping the remote client `ping `, and then check ARP entry `arp` on the local host if it got resolved. If it is `incomplete` for the remote-host-ip, then it means the ping ICMP packet never left the local host machine, the local machine doesn't know where to send the packet. – brokenfoot May 25 '17 at 18:27
  • I'm having troubles to connect to an remote device from my virtual machine. The ping from the host pc to the remote device was succesfull, but when I ping from the virtual device to the remote device I get the "replay from...Destination host unreachable" and like @brokenfoot said, the ARP table inside the virtual machine has no entry with the remote IP. How to fix? – Belekz Jan 19 '18 at 15:47
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    In my case the is ip of the pc I ran the ping from, so calling it "remote" doesn't make sense. And it's not consistent either, one run it pings just fine, next run it shows host unreachable. – vanowm May 15 '20 at 17:41
  • (OP and @vanowm) I found that `Destination Host Unreachable` may actually show up *(tested on ArchLinux)* if arp request didn't get a reply. It may be worth mentioning in the answer, which currently states that "failure of the ARP request" will result in "Request Timed Out" which isn't the case. My testcase: I have two laptops directly connected via ethernet and statically assigned IPs. One has faulty ethernet port requiring you to wiggle cable till connection appears. And sometimes there is a power between the ports, but no packets is actually coming through, resulting in "unreachable" error. – Hi-Angel Mar 27 '23 at 20:07
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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.

Gabriel Graves
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khaos337
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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.

TZHX
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user4667295
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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.

Duncan Jones
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brotox
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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.

northerner
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