I checked my Ubiquiti EdgeRouterX's ARP table and my laptop IP and MAC address were there. I then checked the DHCP lease and my laptop's IP address doesn't expire until tomorrow. I then ran Wireshark on my network and my router sent an ARP message requesting the MAC address of the IP address associated with my laptop. Why would my router send an ARP about an IP address that is not expired and an IP address that has a MAC address already associated with it in the ARP cache table?

  • A lot of vendors send ARPs when STP ages out entries in the MAC address table prematurely during topology changes (Cisco, HPE, Juniper). It is an efficiency technique to stop flooding of unknown unicasts. The idea is that when the host responds to the ARP the switch will now re-learn the MAC address and will no longer flood for that address. Maybe the switch is doing something similar. Can you check the MAC table before an ARP is sent? Does the MAC address exist?
    – user27899
    Jul 27, 2018 at 21:06

1 Answer 1


It turns out my ARP entry expired. I was able to find the command to check how soon ARP entries expire and it turns out mine was set to 60 seconds by default.

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