Port Mirroring; What Ports Can Be Mirrored; How Port Mirroring Works - Alcatel OmniSwitch 6800 Series Network Configuration Manual

Diagnosing Switch Problems

Port Mirroring

You can set up port mirroring for any pair of Ethernet ports within the same switch chassis and across
switches within a stack. Ethernet ports supporting port mirroring include 10BaseT/100BaseTX (RJ-45)
and 1000BaseLX connectors. 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 traf-
fic 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.
Note. A port that is part of an aggregate link cannot be mirrored.
Port mirroring runs in the Chassis Management software and is supported for Ethernet (10 Mbps), Fast
Ethernet (100 Mbps) and Gigabit Ethernet (1000 Mpbs) ports. Up to four (4) port mirroring sessions are
supported in a standalone switch or a stack consisting of two or more switches. However, only one (1)
destination port is supported per standalone switch or stack. Therefore, only 1-to-1, 2-to-1, 3-to-1, and 4-
to-1 configurations are supported in the current release.
Note. Both the mirrored and mirroring ports must be connected and up (enabled) to start mirroring.

What Ports Can Be Mirrored?

OmniSwitch 6800 Series switches support mirroring between any 10/100/1000 port to any other 10/100/
100 port and between any SFP to any other SFP port.

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.
OmniSwitch 6800 Series Network Configuration Guide November 2004
Port Mirroring
page 24-9