2.1.g Implement and troubleshoot other LAN switching technologies

2.1.g [i] SPAN, RSPAN, ERSPAN

SPAN copies traffic from one or more ports, one or more EtherChannels, or one or more VLANs, and sends the copied traffic to one or more destinations for analysis by a network analyzer such as a SwitchProbe device or other Remote Monitoring (RMON) probe.

RSPAN supports source ports, source VLANs, and destinations on different switches, which provides remote monitoring of multiple switches across your network. RSPAN uses a Layer 2 VLAN to carry SPAN traffic between switches . RSPAN consists of an RSPAN source session, an RSPAN VLAN, and an RSPAN destination session. You separately configure RSPAN source sessions and destination sessions on different switches. To configure an RSPAN source session on one switch, you associate a set of source ports or VLANs with an RSPAN VLAN. To configure an RSPAN destination session on another switch, you associate the destinations with the RSPAN VLAN.

Simply put, ERSPAN is RSPAN over GRE. ERSPAN supports source ports, source VLANs, and destinations on different switches, which provides remote monitoring of multiple switches across your network. ERSPAN uses a GRE tunnel to carry traffic between switches. ERSPAN consists of an ERSPAN source session, routable ERSPAN GRE-encapsulated traffic, and an ERSPAN destination session. You separately configure ERSPAN source sessions and destination sessions on different switches. To configure an ERSPAN source session on one switch, you associate a set of source ports or VLANs with a destination IP address, ERSPAN ID number, and optionally with a VRF name . To configure an ERSPAN destination session on another switch, you associate the destinations with the source IP address, ERSPAN ID number, and optionally with a VRF name.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1848-1851).  . Kindle Edition.

http://www.cisco.com/c/en/us/td/docs/switches/lan/catalyst6500/ios/15-0SY/configuration/guide/15_0_sy_swcg/span_rspan_erspan.html