Static ARP (Address Resolution Protocol) entries reduce ARP processing and preclude man-in-the-middle attacks for the specified addresses.
Using Web GUI
Go to Network > Interfaces > Ethernet
Select the appropriate L3 interface.
Click Advanced
Click ARP Entries
Click Add and add the desired entry
Click OK and commit the configuration.
Using Command Line
> configure
# set network interface ethernet ethernet1/2 layer3 arp 10.10.10.1 hw-address F0:1F:FA:02:96:74
# commit