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20-7
Catalyst 2950 Desktop Switch Software Configuration Guide
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Chapter 20 Configuring SPAN and RSPAN
Configuring SPAN
Configuring SPAN
This section describes how to configure SPAN on your switch. It contains this configuration information:
• SPAN Configuration Guidelines, page 20-7
• Creating a SPAN Session and Specifying Ports to Monitor, page 20-7
• Removing Ports from a SPAN Session, page 20-9
SPAN Configuration Guidelines
Follow these guidelines when configuring SPAN:
• SPAN sessions can coexist with RSPAN sessions within the limits described in the “SPAN and
RSPAN Session Limits” section on page 20-6.
• 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 SPAN source ports, you can monitor sent 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.
• 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.
• 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 the destination port are enabled.
Creating a SPAN Session and Specifying Ports to Monitor
Beginning in privileged EXEC mode, follow these steps to create a SPAN session and specify the source
(monitored) and destination (monitoring) ports:
Command Purpose
Step 1
configure terminal Enter global configuration mode.
Step 2
no monitor session {session_number | all |
local | remote}
Clear any existing SPAN configuration for the session.
For session_number, specify 1.
Specify all to remove all SPAN sessions, local to remove all local
sessions, or remote to remove all remote SPAN sessions.