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Catalyst 3750-X and 3560-X Switch Software Configuration Guide
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Chapter 32 Configuring SPAN and RSPAN
Understanding SPAN and RSPAN
• VLAN and trunking—You can modify VLAN membership or trunk settings for source or
destination ports at any time. However, changes in VLAN membership or trunk settings for a
destination port do not take effect until you remove the SPAN destination configuration. Changes in
VLAN membership or trunk settings for a source port immediately take effect, and the respective
SPAN sessions automatically adjust accordingly.
• EtherChannel—You can configure an EtherChannel group as a source port but not as a SPAN
destination port. When a group is configured as a SPAN source, the entire group is monitored.
If a physical port is added to a monitored EtherChannel group, the new port is added to the SPAN
source port list. If a port is removed from a monitored EtherChannel group, it is automatically
removed from the source port list.
A physical port that belongs to an EtherChannel group can be configured as a SPAN source port and
still be a part of the EtherChannel. In this case, data from the physical port is monitored as it
participates in the EtherChannel. However, if a physical port that belongs to an EtherChannel group
is configured as a SPAN destination, it is removed from the group. After the port is removed from
the SPAN session, it rejoins the EtherChannel group. Ports removed from an EtherChannel group
remain members of the group, but they are in the inactive or suspended state.
If a physical port that belongs to an EtherChannel group is a destination port and the EtherChannel
group is a source, the port is removed from the EtherChannel group and from the list of monitored
ports.
• Multicast traffic can be monitored. For egress and ingress port monitoring, only a single unedited
packet is sent to the SPAN destination port. It does not reflect the number of times the multicast
packet is sent.
• A private-VLAN port cannot be a SPAN destination port.
• A secure port cannot be a SPAN destination port.
For SPAN sessions, do not enable port security on ports with monitored egress when ingress
forwarding is enabled on the destination port. For RSPAN source sessions, do not enable port
security on any ports with monitored egress.
• An IEEE 802.1x port can be a SPAN source port. You can enable IEEE 802.1x on a port that is a
SPAN destination port; however, IEEE 802.1x is disabled until the port is removed as a SPAN
destination.
For SPAN sessions, do not enable IEEE 802.1x on ports with monitored egress when ingress
forwarding is enabled on the destination port. For RSPAN source sessions, do not enable
IEEE 802.1x on any ports that are egress monitored.
SPAN and RSPAN and Switch Stacks
Because the stack of switches is treated as one logical switch, local SPAN source ports and destination
ports can be in different switches in the stack. Therefore, the addition or deletion of switches in the stack
can affect a local SPAN session, as well as an RSPAN source or destination session. An active session
can become inactive when a switch is removed from the stack or an inactive session can become active
when a switch is added to the stack.
For more information about switch stacks, see Chapter 5, “Managing Switch Stacks.”