8 thoughts on “Clear or Flush Arp Cache in OS X

  1. Louie_de_palma

    I tried using “arp -a -d” and indeed it stated that each entry was deleted, however the cache was full when doing an “arp -a” right after. No requests made to stations that should of prompted an ARP. I checked with Wireshark and then to be sure I disconnected a node that was in the cache, I then flushed the cache but it is still there???? Baffling…

  2. Sean Fisk

    @Louie_de_palma Got the same results as you did. I didn’t use Wireshark, but again, I didn’t do anything that would have prompted a request. I also ran arp -a -d; arp -a (delete cache then immediately show cache) with the same results. I’m confused too.

  3. Louie_de_palma

    I forgot about this but will be happy of someone provides an answer. At least it’s not just me…

    1. someone

      hi there,

      the arp cache should be filled up with the information of the
      established connections. Please compare to the output of:
      netstat | fgrep ESTABLISHED


  4. Sake

    Hi, I ran into the same problem. Google brought me here, but I was not able to find a solution. So I started to experiment. It seems that OS/X will not delete an arp entry unless you specify which interface to delete it from (at least on my Snow Leopard).

    So you can use "sudo arp -d ifscope en1" or equivalent 🙂

    1. Juan

      According to the man page for arp, the correct order of options are as follow:

      arp -d -a

      This way arp will delete (-d) all the entries that are listed (-a).

  5. TheRealScottMiller

    When is your birthday? I’m trying to figure out if you’re me but from an alternate universe.


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