Port Mirroring - Alcatel-Lucent OmniSwitch 9900 Series Network Configuration Manual

Diagnosing Switch Problems

Port Mirroring

On chassis-based or standalone switches, you can set up port mirroring sessions between Ethernet ports
within the same switch.
All Ethernet ports support port mirroring. When port mirroring is enabled, the active "mirrored" port
transmits and receives network traffic normally, and the "mirroring" port receives a copy of all transmit
and receive traffic to the active port. You can connect an RMON probe or network analysis device to the
mirroring port to see an exact duplication of traffic on the mirrored port without disrupting network traffic
to and from the mirrored port.
Port mirroring runs in the Chassis Management software and is supported for Ethernet ports. In addition,
the switch supports "N-to-1" port mirroring, where up to 128 source ports can be mirrored to a single
destination port.
Refer to the Port Mirroring Specifications Table in the
number of mirroring sessions supported.
What Ports Can Be Mirrored?
Mirroring between any similar ports and between any SFP to any other SFP port is supported.
How Port Mirroring Works
When a frame is received on a mirrored port, it is copied and sent to the mirroring port. The received
frame is actually transmitted twice across the switch backplane–once for normal bridging and then again
to the mirroring port.
When a frame is transmitted by the mirrored port, a copy of the frame is made, tagged with the mirroring
port as the destination, and sent back over the switch backplane to the mirroring port. The diagram below
illustrates the data flow between the mirrored and mirroring ports.
Note. When port mirroring is enabled, there may be some performance degradation, since all frames
received and transmitted by the mirrored port need to be copied and sent to the mirroring port.
OmniSwitch AOS Release 8 Network Configuration Guide
"Port Mirroring Overview" on page 34-3
December 2017
Port Mirroring
for the
page 34-9