Port mirroring on C5 is pretty easy, below is example – mirroring 2 ports ge.1.1 and ge.1.2 as a source and 1.8 a destination.
(su)->set port mirroring create ge.1.1-2 ge.1.8
(su)->show port mirroring
Port Mirroring
==============
Source Port = ge.1.1
Target Port = ge.1.8
Frames Mirrored = Rx and Tx
Port Mirroring status enabled
Source Port = ge.1.2
Target Port = ge.1.8
Frames Mirrored = Rx and Tx
Port Mirroring status enabled
dzbanek 2013-03-05