I don’t have the log information at hand and the incident I worked on was a year or so ago (which is why the screenshot image I shared has the old styling). I know this firewall rule solved the problem we had. If I remember it right, the initial DHCP acquisition by way of broadcast worked fine. Later, the renewal which happens by unicast was blocked, so at the end of the lease time the IP was released. When the IP was released, this caused several services on the server to go berserk (technically speaking!) and it never recovered. What I would expect to happen is for the DHCP client to start over with a broadcast to get a new lease, but that didn’t happen.