HP A7533A - Brocade 4Gb SAN Switch Base Administrator's Manual page 320

The switchShow command output shows the mirror port as shown in the following example.
switch:admin> switchshow
switchName:ESS118
switchType: 42.2
switchState: Online
switchMode: Native
switchRole:Subordinate
switchDomain:
switchWwn:10:00:00:60:69:e4:00:a0
zoning:ON (c)
switchBeacon:
Area Slot Port Media Speed State
=====================================
16 2 0 --N4
17 2 1 idN2
18 2 2 idN2
19 2 3 idN2
20 2 4 --N4
21 2 5 idN2
22 2 6 idN2
23 2 7 idN2
24 2 8 idN1
(output truncated)
156 2 28 --N4
157 2 29 idN2
158 2 30 --N4
159 2 31 idN2
332 Troubleshooting
121 switchId:fffc79
OFF blade2 Beacon: OFF
No_Module
No_Light
No_Light
No_Light
No_Module
No_Light
No_Light
No_Light
OnlineL_Port
No_Module
No_Light
No_Module
OnlineMirror Port