For ARP on IRB interface, when the MAC hits it's age time, an ​ARP request is triggered.

For example, if there is no traffic for the MAC table, ARP requests are sent out every 300 seconds. This is due to the default 'mac-table-aging-time' of 300 seconds, causing the aged out MAC to flush matching ARP entries.

This behavior is working as expected for the IRB interface.