@alanlai88:
If I want fxp1 bridge with fxp0, fxp1 will use DHCP automatically because of fxp0 is using DHCP, am I right?
DHCP will be enabled on fxp1 when fxp1 is bridged to fxp0 and DHCP is enabled on fxp0. DHCP on workstation B is configured entirely independently.
@alanlai88:
Firewall rule on fxp1 already set to any to any.
There are more than two parameters in a firewall rule (protocol, source IP, source port, destination IP, destination port etc). Firewall rules described as "any to any" won't necessarily pass DHCP requests. For example, protocol=TCP, source IP=any, source port=any, destination IP=any, destination port=any won't pass DHCP traffic. Also, preceding rules are important because the first rule to match a packet determines what happens to the packet.
I suggest you reboot workstation B, see what IP address it has and if the IP address is in the DHCP range. If the IP address is out of the DHCP assigned range take a look in the firewall log (Status -> System logs, click on the Firewall tab) to see if the firewall blocked the request.