Cisco Catalyst 2960 Series, Configuration Manual

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• A destination port that belongs to a source VLAN of any SPAN session is excluded from the source list
and is not monitored.
• The maximum number of destination ports in a switch or switch stack is 64.
Local SPAN and RSPAN destination ports function differently with VLAN tagging and encapsulation:
• For local SPAN, if the encapsulation replicate keywords are specified for the destination port, these
packets appear with the original encapsulation (untagged, ISL, or IEEE 802.1Q). If these keywords are
not specified, packets appear in the untagged format. Therefore, the output of a local SPAN session with
encapsulation replicate enabled can contain a mixture of untagged, ISL, or IEEE 802.1Q-tagged packets.
• For RSPAN, the original VLAN ID is lost because it is overwritten by the RSPAN VLAN identification.
Therefore, all packets appear on the destination port as untagged.
RSPAN VLAN
The RSPAN VLAN carries SPAN traffic between RSPAN source and destination sessions. RSPAN VLAN
has these special characteristics:
• All traffic in the RSPAN VLAN is always flooded.
• No MAC address learning occurs on the RSPAN VLAN.
• RSPAN VLAN traffic only flows on trunk ports.
• RSPAN VLANs must be configured in VLAN configuration mode by using the remote-span VLAN
configuration mode command.
• STP can run on RSPAN VLAN trunks but not on SPAN destination ports.
• An RSPAN VLAN cannot be a private-VLAN primary or secondary VLAN.
For VLANs 1 to 1005 that are visible to VLAN Trunking Protocol (VTP), the VLAN ID and its associated
RSPAN characteristic are propagated by VTP. If you assign an RSPAN VLAN ID in the extended VLAN
range (1006 to 4094), you must manually configure all intermediate switches.
It is normal to have multiple RSPAN VLANs in a network at the same time with each RSPAN VLAN defining
a network-wide RSPAN session. That is, multiple RSPAN source sessions anywhere in the network can
contribute packets to the RSPAN session. It is also possible to have multiple RSPAN destination sessions
throughout the network, monitoring the same RSPAN VLAN and presenting traffic to the user. The RSPAN
VLAN ID separates the sessions.
Related Topics
Creating an RSPAN Source Session, on page 492
Creating an RSPAN Destination Session, on page 496
Creating an RSPAN Destination Session and Configuring Incoming Traffic, on page 499
Examples: Creating an RSPAN VLAN, on page 503
SPAN and RSPAN Interaction with Other Features
SPAN interacts with these features:
• Routing — SPAN does not monitor routed traffic. VSPAN only monitors traffic that enters or exits the
switch, not traffic that is routed between VLANs. For example, if a VLAN is being Rx-monitored and
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Information About SPAN and RSPAN