Cisco Catalyst 2950 - Configuring SPAN; SPAN Configuration Guidelines; Creating a SPAN Session and Specifying Ports to Monitor; Removing Ports from a SPAN Session

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Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 10 Configuring the Switch Ports
Configuring SPAN
Configuring SPAN
This section describes how to configure SPAN on your switch and contains this information:
• SPAN Configuration Guidelines, page 10-22
• CreatingaSPANSessionandSpecifyingPortstoMonitor,page10-23
• Removing Ports from a SPAN Session, page 10-24
• Displaying SPAN Status, page 10-25
SPAN Configuration Guidelines
Follow these guidelines when configuring SPAN:
• SPAN is disabled by default.
• Use a network analyzer to monitor ports.
• Only one SPAN sessions can be active on a switch at the same time.
• The destination port cannot be a source port; a source port cannot be a destination port.
• You can have only one destination port.
• An EtherChannel port can be a SPAN source port; it cannot be a SPAN destination port.
• For a SPAN source port, you can monitor transmitted and received traffic for a single port or for a
series or range of ports.
• When you configure a switch port as a SPAN destination port, it is no longer a normal switch port;
only monitored traffic passes through the SPAN destination port.
• When you specify a single source port and do not specify a traffic type (Tx, Rx, or both), both is the
default.
• You can configure a disabled port to be a source or destination port, but the SPAN function does not
start until the destination port and at least one source port is enabled.
• The no monitor session session_number global configuration command removes a source or
destination port from the SPAN session from the SPAN session. If you do not specify any options
following the no monitor session session_number command, the entire SPAN session is removed.
• A SPAN destination port never participates in any VLAN spanning tree. SPAN does include BPDUs
in the monitored traffic, so any spanning-tree BPDUs received on the SPAN destination port for a
SPAN session were copied from the SPAN source ports.
• When SPAN is enabled, configuration changes have these results:
– If you change the VLAN configuration of a destination port, the change is not effective until
SPAN is disabled.
– If you disable all source ports or the destination port, the SPAN function stops until both a
source and destination port are enabled.