Manual

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Chapter 37 RSPAN Configuration
37.1 Introduction to RSPAN
Port mirroring refers to the duplication of data frames sent/received on a port to another port.
The duplicated port is referred to as mirror source port and the duplicating port is referred to as
mirror destination port. It is more convenience for network administrator to monitor and
manage the network and diagnostic after the mirroring function achieved. But it only used for
such instance that the mirror source port and the mirror destination ports are located in the
same switch.
RSPAN (remote switched port analyzer) refers to remote port mirroring. It eliminates the
limitation that the source port and the destination port must be located on the same switch.
This feature makes it possible for the source port and the destination port to be located on
different devices in the network, and facilitates the network administrator to manage remote
switches. It can’t forward traffic flows on remote mirror VLAN.
There are three types of switches with the RSPAN enabled:
1. Source switch: The switch to which the monitored port belongs. The source switch copies
the mirrored traffic flows to the Remote VLAN, and then through Layer 2 forwarding, the
mirrored flows are sent to an intermediate switch or destination switch.
2. Intermediate switch: Switches between the source switch and destination switch on the
network. Intermediate switch forwards mirrored flows to the next intermediate switch or the
destination switch. Circumstances can occur where no intermediate switch is present, if a
direct connection exists between the source and destination switches.
3. Destination switch: The switch to which the destination port for remote mirroring belongs. It
forwards mirrored flows it received from the Remote VLAN to the monitoring device through
the destination port.
When configuring the RSPAN mirroring of the source switch, reflector port mode or destination
mirror port mode can be selected. The destination switch will redirect all the data frames in the
RSPAN VLAN to the RSPAN destination port. For RSPAN mirroring, normal mode and
advanced mode can be chosen, normal is introduced by default and fit the normal user. The
advanced mode fit the advanced user.
1. Advanced mode: To redirect data frames in RSPAN VLAN to the RSPAN destination port,
the intermediary and destination devices should support the redirection of flow.
2. Normal mode: To configure the RSPAN destination port in the RSPAN VLAN. Thus,
datagrams in the RSPAN VLAN will be broadcasted to the destination port. In this mode, the
destination port should be in RSPAN VLAN, and the source port should not be configured for
broadcasting storm control. TRUNK ports should be configured carefully in order not to forward
RSPAN datagrams to external networks. The normal mode has the benefit of easy