Local Switched Port Analyzer

Switched Port Analyzer (SPAN) allows for a protocol analyzer such as a sniffer to passively inspect traffic generated by a VLAN(s) or specific source port(s). SPAN is flexible enough that the source can be a single port or multiple ports, or VLAN traffic copied to a user-defined SPAN destination port. For example, any traffic that is received or transmitted by ports 10/3-5 is also forwarded to port 10/1. (See Example 12-11.) The source and destination port must be on the same switch for SPAN, also known as Local SPAN.

Example 12-11. Monitoring Multiple Ports
Switch1 (enable) set span 10/3-5 10/1
Destination     : Port 10/1
Admin Source    : Port 10/3-5 
!List of all ports that are monitored
Oper Source     : Port 10/3 
!List ...

Get Cisco LAN Switching Fundamentals now with the O’Reilly learning platform.

O’Reilly members experience books, live events, courses curated by job role, and more from O’Reilly and nearly 200 top publishers.