Alcatel Carrier Internetworking Solutions Omni Switch/Router - Manual (Page 600)

Port Mirroring
Page 19-58
where <slot> is the slot number of the module containing the mirrored port, and <port> is the
port number of the mirrored port. For example, if the Admin Status of a port displayed as
M 3 02
then you would know this port is mirroring traffic for Port 2 on the module in Slot 3.
If a cable is not attached to the Mirrored port, port mirroring will not take place. In this case,
the Mirroring Port reverts back to its normally operational state and will bridge frames as if
port mirroring were disabled.
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.
If you attach an external RMON probe to a mirroring port, that probe must have an IP address
that places it in the same VLAN as the mirrored port. In addition if you change the mirrored
port, then you must again make sure that the RMON probe is in the same VLAN as that new
mirrored port.
Mirrored and Mirroring Ports in Same VLAN
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 from an NMS station that are 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 Mirroring Port receives
the management frames. The illustration on the following page shows this data flow.
Mirrored Port Mirroring Port
RMON Probe
Must be in same VLAN.