Cisco Systems 2950, 2955 Configuring SPAN

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Catalyst 2950 and Catalyst 2955 Switch Software Configuration Guide
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Chapter 24 Configuring SPAN and RSPAN
Configuring SPAN
Default SPAN and RSPAN Configuration
Table 24-1 shows the default SPAN and RSPAN configuration.
Configuring SPAN
This section describes how to configure SPAN on your switch. It contains this configuration information:
• SPAN Configuration Guidelines, page 24-7
• Creating a SPAN Session and Specifying Ports to Monitor, page 24-8
• Creating a SPAN Session and Enabling Ingress Traffic, page 24-9
• Removing Ports from a SPAN Session, page 24-10
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 24-6.
• The destination port cannot be a source port; a source port cannot be a destination port.
• You can have only one destination port per SPAN session. You cannot have two SPAN sessions using
the same 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 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.
Tab l e 24-1 Default SPAN and RSPAN Configuration
Feature Default Setting
SPAN state Disabled.
Source port traffic to monitor Both received and sent traffic (both)
Encapsulation type (destination port) Native form (no encapsulation type header).
Ingress forwarding (destination port) Disabled.