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I was pinging Google last night and one of them came back as DUP(!). I did some reading and I found this in the man pages on ping(8):

Damaged packets are obviously serious cause for alarm and often indicate broken hardware somewhere in the ping packet's path (in the network or in the hosts).

Is this really a cause for serious alarm? if it is what should I do?

This occurred on a Windows 7 PC running Ubuntu Live (14.04) via usb drive. It is plugged into the internet with an Ethernet cable (cat 6?). It is using a PlugLink to connect to the router. I believe the provider is ATT Uverse.

edited to link to the man page referenced.

  • What man page was this from? Googling seems to indicate it was ping(8). – slm Nov 30 '14 at 2:42
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About the only thing you can do is verify that the hardware on your end isn't the source of the potentially faulty hardware. As it states in that quote:

...often indicate broken hardware somewhere in the ping packet's path...

So any piece or hardware or wiring could be faulty between you and the destination. So this would mean there could be a faulty wire in some router/switch that your ping packet traversed through, for example.

Tools such as ethtool can be used to diagnose your network interface card (NIC), triaging your wiring will typically require either a dedicated tester, or by using it continuously and monitoring for any additional DUP packets.

You'll often times see faulty hardware showing up when you look a the stats for a network interface that's using it. For example, on my Ethernet interface I'd see a count for either RX/TX errors if there were any potential faulty hardware.

$ ifconfig -a wlp3s0
wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
...
        RX packets 7617411  bytes 5249125225 (4.8 GiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 6364521  bytes 1498792342 (1.3 GiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

These can be manifested in other ways but typically are a good place to start detecting if there's any "smoke" that you need to pay further attention to.

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