SPAN

1. SPAN port is also known as Mirror port, which that specific port is configured to send the same frame of another port, most of the time used for monitoring. One port is used for data network and the span port is configured to send the same frame in/out of that data port. A computer using software such as packet capture or a monitoring device is plugged into the span port.
2. A collection of span rules claled SPAN session can define one ore more source port, on each port, to monitor frams transmitted in and out of the switch port.
3. VLAN mirror will mirror all port in the vlan
4. Remote SPAN (RSPAN)
   1. Encapsulated RSPAN (ERSPAN) through GRE tunnel

Config terminal
    Monitor session 1 source interface gi1/0/11 -12 rx|tx|both
    Monitor session 1 destination interface gi1/0/21
    Monitor session 2 source vlan 11
    Monitor session 2 destination interface gi1/0/22
Show monitor session all
    Type, soure port, rx, destination port, eapsulation ,incgress, vlan
Show monitor detail
    Source port, rx only, tx only, both,