3Com 4210G Series Configuration Manual page 196

As shown in Figure 12-1, packets on the mirroring port are mirrored to the monitor port for the data
monitoring device to analyze.
Figure 12-1 Local port mirroring implementation
How the device processes packets
Traffic
mirrored to
Mirroring port Monitor port
Monitor port
Mirroring port
PC
Remote port mirroring
Remote port mirroring can mirror all packets but protocol packets.
Remote port mirroring is implemented through the cooperation of a remote source mirroring group and
a remote destination mirroring group as shown
Figure 12-2 Remote port mirroring implementation
Remote mirroring involves the following device roles:
Source device
The source device is the device where the mirroring ports are located. On it, you must create a remote
source mirroring group to hold the mirroring ports.
The source device copies the packets passing through the mirroring ports, broadcasts the packets in
the remote probe VLAN for remote mirroring, and transmits the packets to the next device, which could
be an intermediate device (if any) or the destination device.
Intermediate device
Intermediate devices are devices located in between the source device and the destination device.
An intermediate device forwards mirrored packets to the next intermediate device (if any) or the
destination device.
Data monitoring device
Figure 12-2.
12-2