Switch Port Analyzer or SPAN is a feature of Cisco switches that allows you to copy all traffic from a single or multiple source ports or source VLANs to a destination interface. This copied traffic can be used for various purposes:
- It can be captured by a packet sniffer such as Wireshark and can be later analyzed for troublshooting purposes.
- Traffic can be redirected to an IDS/IPS for security purposes
There are various types of SPAN including:
- SPAN - used when the source and destination interfaces are on the same switch
- RSPAN - used when the source and destination interfaces are on different switches
- ERSPAN - used when source and destination interfaces are in different subnets
A simliar feature to SPAN that is used for routers is the Router IP Traffic Export (RITE) feature.