I have had to use this feature on Brocade hardware stuff. I know how to do this on Cisco devices, but it is the first time I must do on Brocade switches to sniff trafic.
To do this :
FCX(config)# mirror-port ethernet 1/2/4
FCX(config)#interface ethernet 1/2/11
FCX(config-if-e1000-11)# monitor ethernet 1/2/4 both
Hope this tip can help 🙂