When Linux receives a UDP packet originating from a sender having a LAN source IP, will Linux put the source MAC address of this packet along the source IP address into the ARP cache table?

  • Have you tried it? Commented Sep 25, 2017 at 14:58
  • I'm about to try it.
    – thomas
    Commented Sep 25, 2017 at 15:00

1 Answer 1


I tried Linux 4.9 and the answer in this case is no. I crafted an UDP packet with an artificial IP address and MAC address combo, which was received by the Linux-under-Test and displayed correctly by netcat. No ARP entry was created (also no incomplete one) and Linux did not send any ARP request regarding the artificial IP address.

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