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Cisco ME 3400 Ethernet Access Switch Software Configuration Guide
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Chapter 26 Configuring SPAN and RSPAN
Understanding SPAN and RSPAN
• It can be any port type—for example, EtherChannel, Fast Ethernet, Gigabit Ethernet, user network
interface (UNI), network node interface (NNI), enhanced network interface (ENI) and so forth.
• For EtherChannel sources, you can monitor traffic for the entire EtherChannel or individually on a
physical port as it participates in the port channel.
• It can be a routed port, an access port, or a trunk port.
• It cannot be a destination port.
• Source ports can be in the same or different VLANs.
• You can monitor multiple source ports in a single session.
Source VLANs
VLAN-based SPAN (VSPAN) is the monitoring of the network traff ic in one or more VLANs. The SPAN
or RSPAN source interface in VSPAN is a VLAN ID, and traffic is monitored on all the ports for that
VLAN.
VSPAN has these characteristics:
• All active ports in the source VLAN are included as source ports and can be monitored in either or
both directions.
• On a given port, only traffic on the monitored VLAN is sent to the destination port.
• If a destination port belongs to a source VLAN, it is excluded from the source list and is not
monitored.
• If ports are added to or removed from the source VLANs, the traffic on the source VLAN received
by those ports is added to or removed from the sources being monitored.
• You cannot use filter VLANs in the same session with VLAN sources.
• You can monitor only Ethernet VLANs.
VLAN Filtering
When you monitor a trunk port as a source port, by default, all VLANs active on the trunk are monitored.
You can limit SPAN traffic monitoring on trunk source ports to specific VLANs by using VLAN
filtering.
• VLAN filtering applies only to trunk ports.
• VLAN filtering applies only to port-based sessions and is not allowed in sessions with VLAN
sources.
• When a VLAN filter list is specified, only those VLANs in the list are monitored on trunk ports.
• SPAN traffic coming from other port types is not affected b y VLAN fi ltering; that is, all VLAN s are
allowed on other ports.
• VLAN filtering affects only traffic forwarded to the destination SPAN port and does not affect the
switching of normal traffic.
Destination Port
Each local SPAN session or RSPAN destination session must have a destination port (also called a
monitoring port) that receives a copy of traffic from the source ports or VLANs and sends the SPAN
packets to the user, usually a network analyzer.