Allied Telesis AT-S25 - Manual (Page 89)

AT-S25 Management Software User’s Guide
89
Port Mirroring Overview
The port mirroring feature allows you to unobtrusively monitor the
traffic being received and transmitted on a port on a switch by having
the traffic copied to another switch port. You could connect a network
analyzer to the port where the traffic is being copied and monitor the
traffic on the other ports without impacting network performance or
speed.
Observe the following guidelines when creating a port mirror:
❑ The port whose traffic is to be copied is called the source port. The
port where the traffic is to be copied and where the network
analyzer will be located is called the destination port.
❑ You can mirror only one port in a stack at a time.
❑ There can be only one destination port.
❑ The destination port cannot be a member of a port trunk.
❑ The source port and the destination port can be located on
different switches in a stack.
❑ The source port and the destination port must be operating at the
same speed. For example, you cannot use a 10/100 Mbps port to
monitor traffic on a 1000 Mbps GBIC port.
❑ The source port and the destination port must be in the same
VLAN in order to see broadcast, multicast, and flooded traffic on
the destination mirror port. If these packets are being sent and
received on a tagged port, they will have the tag removed before
delivery to the destination mirror port.
❑ Unicast packets that are received on a tagged port will have the
tag removed before delivery to the destination mirror port.
Unicast packets sent out a tagged port will have the tag inserted
before delivery to the destination port.