Port Mirroring; What Ports Can Be Mirrored?; How Port Mirroring Works - Alcatel-Lucent OmniSwitch 6850-48 Network Configuration Manual

Port Mirroring

Port Mirroring
On chassis-based or standalone switches, you can set up port mirroring sessions between Ethernet ports
within the same switch, while on stackable switches, you can set up port mirroring sessions across
switches within the same stack.
Ethernet ports supporting port mirroring include 10BaseT/100BaseTX/1000BaseT (RJ-45), 1000BaseSX/
LX/LH, and 10GBaseS/L (LC) 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 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 (10 Mbps), Fast
Ethernet (100 Mbps), Gigabit Ethernet (1000 Mpbs), and 10 Gigabit Ethernet (10000 Mbps) ports. In addi-
tion, the switch supports "N-to-1" port mirroring, where up to 24 (OmniSwitch 6800) or 128 (OmniSwitch
6400, 6850, 6855, and 9000) source ports can be mirrored to a single destination port.
Note the following restriction when configuring a port mirroring session:
•
Two (2) port mirroring sessions are supported per standalone chassis-based switch or in a stack consist-
ing of two or more switches.
•
You cannot configure a port mirroring and a port monitoring session on the same NI module in an
OmniSwitch chassis-based switch.
•
You cannot configure port mirroring and monitoring on the same switching ASIC on OmniSwitch
6400, 6850, and 6855 switches. Each switching ASIC controls 24 ports (e.g., ports 1–24, 25–48, etc.).
For example, if a port mirroring session is configured for ports 1/12 and 1/22, then configuring a port
monitoring session for any of the ports between 1 and 24 is not allowed.
•
You cannot configure port mirroring and monitoring on the same switching ASIC on OmniSwitch
6800 Series switches. Each switching ASIC controls 12 ports (e.g., ports 1–12, 13–24, etc.). For exam-
ple, if a port mirroring session is configured for ports 1/6 and 1/10, then configuring a port monitoring
session for any of the ports between 1 and 12 is not allowed.
•
If a port mirroring session is configured across two switching ASICs, then configuring a monitoring
session is not allowed on any of the ports controlled by each of the ASICs involved. For example, if a
port mirroring session is configured for ports 1/8 and 1/30 on a 48-port switch, then configuring a port
monitoring session involving any of the ports between 1 and 48 is not allowed.

What Ports Can Be Mirrored?

Mirroring between any 10/100/1000 port to any other 10/100/1000 port 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.
page 45-14 OmniSwitch AOS Release 6 Network Configuration Guide
Diagnosing Switch Problems
September 2009