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Catalyst 3560 Switch Software Configuration Guide
OL-8553-06
Chapter 28 Configuring SPAN and RSPAN
Configuring SPAN and RSPAN
Configuring Local SPAN
These sections contain this configuration information:
• SPAN Configuration Guidelines, page 28-10
• Creating a Local SPAN Session, page 28-11
• Creating a Local SPAN Session and Configuring Incoming Traffic, page 28-13
• Specifying VLANs to Filter, page 28-15

SPAN Configuration Guidelines

Follow these guidelines when configuring SPAN:
• For SPAN sources, you can monitor traffic for a single port or VLAN or a series or range of ports
or VLANs for each session. You cannot mix source ports and source VLANs within a single SPAN
session.
• The destination port cannot be a source port; a source port cannot be a destination port.
• You cannot have two SPAN sessions using the same destination port.
• 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.
• Entering SPAN configuration commands does not remove previously configured SPAN parameters.
You must enter the no monitor session {session_number | all | local | remote} global configuration
command to delete configured SPAN parameters.
• For local SPAN, outgoing packets through the SPAN destination port carry the original
encapsulation headers—untagged, ISL, or IEEE 802.1Q—if the encapsulation replicate keywords
are specified. If the keywords are not specified, the packets are sent in native form. For RSPAN
destination ports, outgoing packets are not tagged.
• 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 or source VLAN are enabled.
• You can limit SPAN traffic to specific VLANs by using the filter vlan keyword. If a trunk port is
being monitored, only traffic on the VLANs specified with this keyword is monitored. By default,
all VLANs are monitored on a trunk port.
• You cannot mix source VLANs and filter VLANs within a single SPAN session.
• Catalyst 3560-24PS and 3560-48PS switches have hardware limitations related to SPAN. An egress
SPAN copy of routed unicast traffic might show an incorrect destination MAC address on both local
and remote SPAN sessions. This limitation does not apply to bridged packets. The workaround for
local SPAN is to use the replicate option.
VLAN filtering On a trunk interface used as a source port, all VLANs are
monitored.
RSPAN VLANs None configured.
Table 28-1 Default SPAN and RSPAN Configuration (continued)
Feature Default Setting