Bridge member where IP isn't assigned can't pass traffic?

[doteater]

Hey folks,

Overview:

I'm trying to bridge 2 LAN interfaces…my goal is to have machines connected to 2 different physical interfaces on the same subnet (192.168.1.1/24).

what I did:
Following documentation here: https://doc.pfsense.org/index.php/Interface_Bridges

I created by bridge, LAN_BRIDGE, with member interfaces LANA and LANB (the 2 physical interfaces).
I configure the LANA interface to be the one with the bridge IP. Both LAN_BRIDGE and LANB are not configured with an IP address (per the instructions)
I also set up the DHCP server on LANA.
For the sake of testing, the firewall is wide open for LAN_BRIDGE, LANA, and LANB. All IPv4 traffic of any protocol is allowed on all 3.

result, troubleshooting
The result is that the machines on LANA and LANB can both get IPs via DHCP, but only LANA seems to be able to pass other traffic, like pinging the gateway. I tried moving the IP configuration and DHCP server from LANA->LAN_BRIDGE, out of curiosity, but that didn't help. Also tried swapping the values of net.link.bridge.pfil_member and net.link.bridge.pfil_bridge, didn't help.

Does it sound like I'm configuring this stuff correctly? Guesses as to what pit I'm falling into? Seems like a really simple bridging setup.
Thanks very much and please let me know if I can provide any more info.