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Port Mirroring Diagnosing Switch Problems
page 27-14 OmniSwitch 6600 Family Network Configuration Guide April 2006
Using Port Mirroring with External RMON Probes
Port mirroring is a helpful monitoring tool when used in conjunction with an external RMON probe. Once
you set up port mirroring, the probe can collect all relevant RMON statistics for traffic on the mirrored
port. You can also move the mirrored port so that the mirroring port receives data from different ports. In
this way, you can roam the switch and monitor traffic at various ports.
Note. If the mirroring port will monitor mirrored traffic on an RMON probe belonging to a different
VLAN than the mirrored port, it should be protected from blocking due to Spanning Tree updates. See
“Unblocking Ports (Protection from Spanning Tree)” on page 27-15 for details.
The following diagram illustrates how port mirroring can be used with an external RMON probe, to copy
RMON probe frames and Management frames to and from the mirroring and mirrored ports. Frames
received from an RMON probe attached to the mirroring port can be seen as being received by the
mirrored port. These frames from the mirroring port are marked as if they are received on the mirrored
port before being sent over the switch backplane to an NMS station. Therefore, management frames
destined for the RMON probe are first forwarded out the mirrored port. After being received on the
mirrored port, copies of the frames are mirrored out the mirroring port—the probe attached to the mirror-
ing port receives the management frames.
OmniSwitch 6648
OmniSwitch 6648
OmniSwitch 6648
OmniSwitch 6648
OmniSwitch
Mirrored Port
Mirroring Port
NMS Workstation
RMON Probe
A. RMON probe frames sent from the mirroring port...
B. ...appear to come from the mirrored port
when the NMS Workstation receives them.
OmniSwitch
Mirrored Port
Mirroring Port
NMS Workstation
RMON Probe
D. ...and port mirroring sends copies of the
Management frames to the mirroring port.
C. Management frames from the NMS Workstation are sent to the mirrored port....
Port Mirroring Using External RMON Probe