I have OPNsense with 4 NICs (2.5 Gbps).
WAN (pppoe0)
LAN_MAIN (10.0.0.1/24)
LAN3_4 (bridge0, 10.0.1.1/24)
DHCP works fine on both, but devices on 10.0.0.x can't ping 10.0.1.x.
OPNsense itself can ping both.
Firewall rules allow any between the two LANs, NAT only on WAN.
No floating blocks.
Still no LAN ping. Any idea what's missing?
Thanks — waiting for your help.
The usual problems would be ARP or gateway. For ARP, check the end clients - "arp -a" on almost any platform. Check the MAC addresses. For gateway, I'd expect you'd want your clients to use OPNsense as their gateway... You could try pinging 10.0.0.1 and 10.0.1.1 from each client, and/or check their routing tables.
I also use the live log to see what's going on in the firewall (I have all rule logging enabled). "Firewall: Diagnostics: Sessions" or "Firewall: Diagnostics: States" might work for you, too.
Did you follow all steps to set up your bridge from here: https://docs.opnsense.org/manual/how-tos/lan_bridge.html, especially step 6?