SPAN (Switch Port Analyzer) is a functionality that mirrors one or more ports or VLANs into another port to be monitored by an IDS (Intrusion detection system).
Local SPAN
monitor session 1 source interface G0/1 both monitor session 1 source interface G0/2 both monitor session 1 destination interface G0/5
Remote SPAN
vlan 99 remote-span name Remote_Span monitor session 1 source interface G0/2 monitor session 1 destination remote vlan 99 reflector-port G0/5 vlan 99 remote-span name Remote_Span monitor session 1 source remote vlan 99 monitor session 1 destination interface G0/1
Monitoring
do show monitor do show monitor session 1 do show monitor session 1 detail