When doing changes on your network, in ex. giving known hosts new IP’s or giving new servers the IP’s of the old ones, there will be a need to reset the ARP table to make sure that traffic can traverse the firewall again, this can be done by reboot’s or but doing a SSH conenction to the firewall and type this in root mode:
“ip -s -s neigh flush all”
On UTM:
Yoiu can also show the ARP entries currently in the system with command “arp -n”
The above command will also work on Sophos XG firewall in the shell, however it has a gui for the same:
Source: Sophos XG Firewall: How to Flush the Neighbor Cache
