Why does the ARP table in the gateway device contain no entry for a changed switch MAC address?

Aruba Employee
Aruba Employee

Product and Software: This article applies to all Aruba controllers and ArubaOS 2.x and 3.x.


When the MAC address of a switch has changed, an update for the controller's MAC address should be sent to the ARP table in the router or switch (gateway device). The update generally occurs with a protocol GARP.


Generally, all Windows devices and network devices support GARP, and Aruba controllers support GARP, so the gateway should accept the GARP updates in its ARP table.


(GARP is the packet that devices send when they update the ARP table on all devices on the same subnet.)

In rare instances, we may find that a controller changed its MAC address and the changes are not reflected on the gateway. However, Aruba controllers support GARP, so the issues are not with the Aruba devices and we need to check whether the gateway device is not entertaining GARP.


If GARP is not updating the ARP table, you can try either of these steps:

  •        Wait for the default ARP timer to expire and the ARP table is updated.
  •         Clear the ARP table manually so that it repolls and reregisters the MAC address of the controllers.

Note: After spanning tree completes its process, no other GARP updates should occur. GARP should send an update only after spanning tree opens the port.


For further information, please contact Support.

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‎07-09-2014 01:49 PM
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