20 CONFIGURATION FOR QOS FEATURES
RSPAN Features Remote switched port analyzer (RSPAN) refers to remote port mirroring. It breaks
through the limitation that the mirrored port and the mirroring port have to be
located in the same switch, and makes it possible that the mirrored and mirroring
ports be located across several devices in the network, and greatly enhances the way
that the network administrator can manage the switch.
The application of RSPAN is illustrated in Figure101.
Figure101 RSPAN application
There are three types of switches with the RSPAN enabled.
■Source switch: the switch to which the monitored port belong.
■Intermediate switch: the switches that are between the source and destination
switches on the network.
■Destination switch: the switch to which the remote mirroring destination port
belong.
Table403 gives an illustration of how various ports are involved in the mirroring
operation.
Table403 The ports involved in the mirroring
Switch
The ports
involved Function
Source switch Source port The port to be mirrored. By means of local port
mirroring, the users’ data packets can be copied to the
reflector port. There could be more than one source
port.
Reflector port Receive users’ data packets that are mirrored on a local
port.
Trunk port Send the mirrored packets to the intermediate switch
or the destination switch.
Intermediate
switch
Trunk port Send the mirrored packets to the destination switch.
Two Trunk ports are necessary for the intermediate
switch in order to connect with devices from both the
source and destination switches.
Destination switch Trunk port Receive remote mirrored packets.
Destination port Monitor the remote mirrored packets