pfSense

This also seems to have a negative effect on switches the pfSense gateway is not directly connected to. I.e. pfSense lives on my "core" switch. I have 2 other switches connected to that switch. The switches have problems locating 00:00:5e:00:01:01 and flood every frame destined to that address to all switchports. That also applies to WLAN APs connected to those switches and this is where it gets problematic for WLAN performance.
The fix does not seem to have made it to 2.4 beta yet it seems, would be great if it could be implemented to beta test it.

We have the same problems in our setup.

A switch is connected to two pfsense firewalls with a CARP setup. Since the pfsense sends the packets with the wrong (imho) MAC src, the switch never updates his source address table for the virtual MAC of the CARP IP. Therefore, all packets with destination Firewall (CARP IP/CARP MAC) are always flooded on the network!

We're using pfsense in version 2.3.3. The option net.link.ether.inet.carp_mac is set to 1, but the src mac is still wrong.

Update: What I forgot to mention is that it doesn't only affect ARP requests/replies, but all traffic.