3Com calls the port mirror feature "roving analysis". Here is an example for a SS II Switch 3300 (your entries are displayed in red:
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Menu options: --------------3Com SuperStack II Switch 3300--------------
bridge - Administer bridging/VLANS
ethernet - Administer Ethernet ports
feature - Administer system features
ip - Administer IP
logout - Logout of the Command Line Interface
snmp - Administer SNMP
system - Administer system-level functions
Type ? for help.
-----------------------------------Switch 3300 (1)----------------------
Select menu option: feature
Menu options: --------------3Com SuperStack II Switch 3300--------------
analyzer - Administer Roving Analysis
broadcastStormCont - Enable/Disable Broadcast Storm Control
resilience - Administer resilient links
trunk - Administer trunks
Type "q" to return to the previous menu or ? for help.
-----------------------------------Switch 3300 (1)----------------------
Select menu option (feature): analyzer
Menu options: --------------3Com SuperStack II Switch 3300--------------
add - Configure the roving analysis port
display - Display the Roving Analysis configuration
remove - Clear the roving analysis port
start - Start monitoring
stop - Stop monitoring
Type "q" to return to the previous menu or ? for help.
-----------------------------------Switch 3300 (1)----------------------
Select menu option (feature/analyzer): add
Select analysis unit (1): 1
Enter analysis port
(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25): 1
Select menu option (feature/analyzer): start
Select unit to monitor (1): 1
Enter port to monitor
(2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25): 25
Select menu option (feature/analyzer): display
Roving Analysis Configuration
Monitor Port Analysis Port State
Unit 1 Port 25 Unit 1 Port 1 Enabled
Select menu option (feature/analyzer):
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Cheers *Rob