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I know the ARP table is cached data.

On Juniper, we can use show arp to query the arp table:

admin@juniper> show arp | match "16.23.43.75"                               
ac:1f:6b:90:d1:ca 16.23.43.75   16.23.43.75             ae16.83             
    none  

But the arp is not a real-time table, you know.

If we shutdown the 16.23.43.75 server, we can still query out the 16.23.43.75 record.

Is there a way to refresh the arp table in the case do not affect other routing?

  • ARP table entries will eventually time out, and you can probably set he time for that. – Ron Maupin Apr 1 '19 at 14:51
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You can clear the arp table for the interface by issuing clear arp interface ae16.83. This will remove all entries for the interface (which means ARP learning has do be done for all hosts on the interface). If you want to remove one host you can try to use clear arp hostname [IP-Address] and this works sometimes as well. Normally it is not necessary to do this by hand as the entry expires anyway after a while.

| improve this answer | |
  • can you give a example of clear arp hostname [mac-address] ? how can I get a hostname of a server? – 244boy Apr 1 '19 at 10:34
  • Just enter the IP address: clear arp hostname 16.23.43.75 (Edit: I thought it was the MAC-Adress but it's the IP you need to enter) – Sebastian Wiesinger Apr 1 '19 at 10:35
  • will the arp study will affect the network a lot? – 244boy Apr 1 '19 at 11:13
  • no - deleting the ARP will be barely noticeable - it will be re-learnt almost immediately if there are active traffic flows – Benjamin Dale Apr 1 '19 at 13:08

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