Diagnosing Switch Problems Port Mirroring
OmniSwitch AOS Release 8 Network Configuration Guide December 2017 page 34-14
Unblocking Ports (Protection from Spanning Tree)
Spanning tree is disabled by default on an MTP port. When unblocked VLAN is configured , the VLAN 
ID specified is assigned to the MTP port as the default VLAN. Hence allowing inbound traffic and 
handling traffic for that VLAN ID. Spanning tree remains disabled. To create a mirroring session that 
protects the mirroring port from being blocked (default), enter the port-mirroring source destination 
CLI command and include the port mirroring session ID number, source and destination slot/ports, and 
unblocked VLAN ID number, as shown in the following example:
-> port-mirroring 6 source 2/3 destination 2/4 unblocked-vlan 750
This command line specifies mirroring session 6, with the source (mirrored) port located in slot 2/port 3, 
and the destination (mirroring) port located in slot 2/port 4. The mirroring port on VLAN 750 is protected 
from Spanning Tree updates.
Enabling or Disabling Mirroring Status
Mirroring Status is the parameter using which you can enable or disable a mirroring session (i.e., turn port 
mirroring on or off). There are two ways to do this:
• Creating a Mirroring Session and Enabling Mirroring Status or Disabling a Mirroring Session 
(Disabling Mirroring Status). These procedures are described below and on the following page.
• Enabling or Disabling a Port Mirroring Session—“shorthand” versions of the above commands that 
require fewer keystrokes. Only the port mirroring session ID number needs to be specified, rather than 
the entire original command line syntax (e.g., source and destination slot/ports and optional unblocked 
VLAN ID number). See “Enabling or Disabling a Port Mirroring Session (Shorthand)” on page 34-15 
for details.
Disabling a Mirroring Session (Disabling Mirroring Status)
To disable the mirroring status of the configured session between a mirrored port and a mirroring port 
(turning port mirroring off), use the port-mirroring source destination CLI command. Be sure to include 
the port mirroring session ID number and the keyword disable.
In this example, the command specifies port mirroring session 6, with the mirrored (active) port located in 
slot 2/port 3, and the mirroring port located in slot 6/port 4. The mirroring status is disabled (i.e., port 
mirroring is turned off):
-> port-mirroring 6 source disable
Keep in mind that the port mirroring session configuration remains valid, even though port mirroring has 
been turned off. 
Note. You can modify the parameters of a port mirroring session that has been disabled.
Note. The port mirroring session identifier and slot/port locations of the designated interfaces must always 
be specified.