Today I migrated a firewall-configuration from a SG80-Appliance to a 1450er-Appliance (configured everything manually, installed the latest firmware 07/2017). We have a lot of auto-static-nats configured there (are terminateing in the WAN-Interface). Just for clarification, the WAN-Inteface is configured with internal-ips (MPLS-Connection).
After activating the new appliance (same ips and static-nat-ips taken from the old SG80-Appliance) the static-nats did not work, because the old MAC-Addresses of the old SG80-Appliance were stored on the router's arp-table.
But the new MAC of the WAN-Interface was updated immediately. So it seems, that the Firewall does not send out gratuitous arp for static-nat-ips but only for its own IP on the WAN-Interface.
As I said, it was not a problem, but I only want to know, if this is a standard behaviour because today it was the very first time, I did not delete the arp-table for the nat-ips, do not know why.