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Catalyst2950 Desktop Switch Software Configuration Guide
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Chapter20 Configuring SPAN and RSPAN
Understanding SPAN and RSPAN
Source Port
A source port (also called a monitored port) is a switched port that you monitor for network traffic
analysis. In a single local SPAN session or RSPAN source session, you can monitor source port traffic
such as received (Rx), transmitted (Tx), or bidirectional (both). The switch supports any number of
source ports (up to the maximum number of available ports on the switc h) .
A source port has these characteristics:
•It can be any port type (for example, EtherChannel, Fast Ether net, G igab it Eth er net, and so fo rth) .
•It cannot be a destination port.
•Each source port can be configured with a direction (ingr ess, egr ess, o r both) t o mo ni tor. For
EtherChannel sources, the monitored direction would apply to al l the p hysi cal p ort s in the group.
•Source ports can be in the same or different VLANs.
You can configure a trunk port as a source port. All VLANs active on the trunk are monitored.
Destination Port
Each local SPAN session or RSPAN destination session must have a destination port (also called a
monitoring port) that receives a copy of traffic from the source port.
The destination port has these characteristics:
•It must reside on the same switch as the source port (for a local SPAN session).
•It can be any Ethernet physical port.
•It cannot be a source port or a reflector port.
•It cannot be an EtherChannel group or a VLAN.
•It can be a physical port that is assigned to an EtherChannel group, even if the EtherChan nel group
has been specified as a SPAN source. The port is removed from the group while it is configured as
a SPAN destination port.
•When it is active, incoming traffic is disabled. The port does not transmit any traffic except that
required for the SPAN session.
•It does not participate in spanning tree while the SPAN session is active.
•When it is a destination port, it does not participate in any of the Layer 2 protocols (STP, VTP, CDP,
DTP, PagP).
•No address learning occurs on the destination port.
Reflector Port
The reflector port is the mechanism that copies packets onto an RSPAN VLAN. The reflector port
forwards only the traffic from the RSPAN source session with which it is affiliated. Any device
connected to a port set as a reflector port loses connectivity until the RSPAN source session is disabled.
The reflector port has these characteristics:
•It is a port set to loopback.
•It cannot be an EtherChannel group, it does not trunk, and it cannot do protocol filtering.