1-2
To implement remote port mirroring, a special VLAN, called remote-probe VLAN, is needed. All mirrored
packets are sent from the reflector port of the source switch to the monitor port (destination port) of the
destination switch through the remote-probe VLAN, so as to implement the monitoring of packets
received on and sent from the source switch on the destination switch.
Figure 1-2
illustrates the
implementation of remote port mirroring.
Figure 1-2
Remote port mirroring application
The switches involved in the remote port mirroring implementation play the following three roles.
z
Source switch: The monitored port resident switch. It copies traffic to the reflector port, which then
transmits the traffic to an intermediate switch or destination switch through the remote-probe
VLAN.
z
Intermediate switch: Switches between the source switch and destination switch on the network.
An intermediate switch forwards mirrored traffic flows to the next intermediate switch or the
destination switch through the remote-probe VLAN. No intermediate switch is present if the source
and destination switches directly connect to each other.
z
Destination switch: The remote mirroring destination port resident switch. It forwards mirrored
traffic flows it received from the remote-probe VLAN to the monitoring device through the
destination port.
Table 1-1
describes how the ports on various switches are involved in the mirroring operation.
Table 1-1
Ports involved in the mirroring operation
Switch
Ports involved
Function
Source port
Port monitored. It copies packets to the reflector
port through local port mirroring. There can be
more than one source port.
Reflector port
Receives packets from the source port and
broadcasts the packets in the remote-probe
VLAN.
Source switch
Trunk port
Sends mirrored packets to the intermediate
switch or the destination switch.
Intermediate switch
Trunk port
Sends mirrored packets to the destination switch.
Two trunk ports are necessary for the
intermediate switch to connect the devices at the
source switch side and the destination switch
side.
