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Chapter1 Configuring Interfaces and Circuits
Configuring the Switched Port Analyzer Feature
1-44
Cisco Content Services Switch Routing and Bridging Configuration Guide
OL-4580-01
Configuring the Switched Port Analyzer Feature
Configure the switched port analyzer (SPAN) feature on your CSS to mirror
(copy) traffic passing through one CSS port (Fast Ethernet or Gigabit Ethernet) to
another designated port of the same type and on the same CSS module for
analysis. You can use SPAN for network troubleshooting or tuning using a
network analyzer. SPAN is sometimes referred to as port mirroring or port
monitoring.
A SPAN session is the association of a destination port with a source port on the
same CSS module. The port that is monitored is called the source SPAN (SSPAN)
port. An SSPAN port consists of two components:
• Ingress path - Network traffic entering the CSS. The CSS copies to the
monitoring port packets that the SSPAN port receives (SSPAN Rx) from the
network.
• Egress path - Network traffic leaving the CSS. The CSS copies to the
monitoring port packets that the SSPAN port transmits (SSPAN Tx) to the
network.
SPAN can monitor the ingress path, the egress path, or both. You can configure
only one SSPAN port in a CSS chassis.
The port that monitors the SSPAN port is called the destination SPAN (DSPAN)
port. You can configure only one DSPAN port in a CSS chassis and it must have
the following characteristics:
• Same speed as the SSPAN port
• Same media type as the SSPAN port
• Local (physically resides on the same CSS module)
Once you configure a port as a DSPAN port, the CSS removes it from all VLANs
and ignores ingress traffic on that port. In addition, the DSPAN port does not
participate in STP or routing protocols such as RIP and OSPF.
Traffic copied to the DSPAN port is typically forwarded to a network analyzer,
protocol analyzer, or an RMON probe. SPAN allows you to monitor CSS ports
without:
• Disconnecting cables
• Requiring multiple analyzers or probes
• Needing hubs or switches