problem with ARP

i used DHCP Server for all user.
some user assign ip and mac in IP/DHCP Server - Leases. (make static)
when make static in ip/arp for each user. (for assign mac to ip )

but I get an error message:

“could not add new ARP already have mapping for this ip”

(attachment)
ARP-1.jpg
ARP1.jpg

Up!