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Is there any logical explanation for this output? I can understand all of the three different results, but all three in one single run of PING? Could my router be defective? I have no internet connection problems, just connection to other machine on my network.

C:\PING 192.168.1.37
Pinging 192.168.1.37 with 32 bytes of data:

Reply from 192.168.1.37: bytes=32 time<1ms TTL=128
Request timed out.
Request timed out.
Reply from 192.168.1.35: Destination host unreachable.

The next run might show any other combination. Including all 4 success, all 4 host unreachable or all 4 timed out. Seems like random behavior.

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2 Answers 2

Ping works by sending a series of packets. In this case ping have sent three packets. For the first one it had a reply from the target host. For the second one, no reply at all. For the third one, no reply from the host, but a notification packet arrived from a different host saying "I can't route your packet, the destination address looks like it is on my subnet, but I can't ARP it". The host notyfying could be your own host.

So you have an unstable connection to the host. Not all packets arrive there or not all packets return, but some make it. If this host is on your LAN, this may be a switch failure, cable failure, or NIC failure.

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"Destination host unreachable" is an ICMP message generated by a router when it believes it has a message for a local network but it can't find a host to claim that message.

When the first ping hits the router nearest to the destination, that router begins sending ARP request packets on its local network, asking for the MAC address of a host with an IP address matching the ping's destination. While the router is waiting for a response, the pings timeout. Only once the ARP times out does the router decide the host is not reachable.

At that point it caches the result and begins sending back the ICMP Destination host unreachable messages to any new network traffic that comes along. Exactly how long it will cache the ARP failure depends on the router.

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