Cisco Systems 3750E manual Source VLANs, Vlan Filtering, 30-7

Chapter 30 Configuring SPAN and RSPAN

Understanding SPAN and RSPAN

A source port has these characteristics:

•It can be monitored in multiple SPAN sessions.

•Each source port can be configured with a direction (ingress, egress, or both) to monitor.

•It can be any port type (for example, EtherChannel, Gigabit Ethernet, 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 an access port, trunk port, routed port, or voice VLAN 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 traffic 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 or to voice VLAN 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 or on voice VLAN access ports.

•SPAN traffic coming from other port types is not affected by VLAN filtering; that is, all VLANs 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.

Catalyst 3750-E and 3560-E Switch Software Configuration Guide

OL-9775-02 30-7