Bridging

Base Configuration

config# bridge 50 protocol ieee
config-if# bridge-group 50
config# bridge 50 priority 0...65535 (do that at a frame-relay hub to make it the STP root) 

Bridge Virtual Interfaces

config# bridge irb (enable integrated routing & bridging)
config# interface bvi 50 (match bridge ID)
config-if# ip address
config# bridge 50 bridge ip
config# bridge 50 route ip

IP Helper Address

config-if# ip helper-address 192.168.2.255 (forward to broadcast address)
config-if# ip directed-broadcast (all broadcasts)
config# no ip forward-protocol udp (remove all udp ports from forwarding)
config# ip forward-protocol udp 137 (only forward specific udp port)

View/Debug Commands

show bridge
show spanning-tree
show interface irb