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Catalyst 3750 Metro Switch Software Configuration Guide
78-15870-01
Chapter 21 Configuring SPAN and RSPAN
Understanding SPAN and RSPAN
This section includes these topics:
• Local SPAN, page 21-2
• Remote SPAN, page 21-2
• SPAN and RSPAN Concepts and Terminology, page 21-3
• SPAN and RSPAN Interaction with Other Features, page 21-8
Local SPAN
Local SPAN supports a SPAN session entirely within one switch; all source ports or source VLANs and
destination ports reside in the same switch. Local SPAN copies traffic from one or more source ports in
any VLAN or from one or more VLANs to a destination port for analysis. For example, in Figure 21-1,
all traffic on port 5 (the source port) is mirrored to port 10 (the destination port). A network analyzer on
port 10 receives all network traffic from port 5 without being physically attached to port 5.
Figure 21-1 Example of Local SPAN Configuration on a Switch
Remote SPAN
RSPAN supports source ports, source VLANs, and destination ports on different switches, enabling
remote monitoring of multiple switches across your network. The traffic for each RSPAN session is
carried over a user-specified RSPAN VLAN that is dedicated for that RSPAN session in all participating
switches. The RSPAN traffic from the source ports or VLANs is copied into the RSPAN VLAN and
forwarded over trunk ports carrying the RSPAN VLAN to a destination session monitoring the RSPAN
VLAN. Each RSPAN source switch must have either ports or VLANs as RSPAN sources. The
destination is always a physical port.
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Port 5 traffic mirrored
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Network analyzer
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