I have a bridge between two networks using the same address space, and have very strange issues with ARP packets.
Interface bridge0 has no IP address assigned, and has two members : em1 and em2.
A virtual machine on em2 interface side is sending ARP requests, asking for physical address of gateway that is on em1 interface side but the replies are only to be seen on em1, not getting forwarded to the machine.
em1
11:20:59.121901 00:50:56:b8:13:53 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 192.168.22.254 (ff:ff:ff:ff:ff:ff) tell 192.168.22.204, length 46
11:20:59.122067 00:50:56:b8:13:53 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 192.168.22.254 (ff:ff:ff:ff:ff:ff) tell 192.168.22.204, length 46
11:20:59.122780 00:00:0c:9f:f1:e2 > 00:50:56:b8:13:53, ethertype ARP (0x0806), length 60: Reply 192.168.22.254 is-at 00:00:0c:9f:f1:e2, length 46
em2
11:20:59.121884 00:50:56:b8:13:53 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 192.168.22.254 (ff:ff:ff:ff:ff:ff) tell 192.168.22.204, length 46
11:20:59.122079 00:50:56:b8:13:53 > ff:ff:ff:ff:ff:ff, ethertype ARP (0x0806), length 60: Request who-has 192.168.22.254 (ff:ff:ff:ff:ff:ff) tell 192.168.22.204, length 46
Both pf and IPFW firewalls are disabled, I'm using 10.3-RELEASE