SPAN (Switched Port Analyzer) is a Cisco Proprietary feature which allows to send a copy of traffic passing through ports to another port on the switch.As demand on deep packet inspection and analysis grew , so did the development on SPAN and Cisco cam up with RSPAN and ERSPAN. While SPAN is limited to local switch , RSPAN (Remote SPAN) and ERSPAN (Encapsulated RSPAN) mirroring ports in one switch to a port in different switch.
Both RSPAN and ERSPAN support source ports, source VLANs, and destinations on different switches, which provides remote monitoring of multiple switches across network.Both belong to the SPAN family and are Cisco proprietary.However , being extensions of SPAN technology , RSPAN and ERSPAN tend to differ. Below table enlists some of their distinctions –
Related- Introduction to RSPAN, SPAN and ERSPAN