How to configure SPAN or Port Mirroring on a Cisco Router or Switch

Pre-requisites 

• Basic Cisco command-line knowledge

Scenarios

Scenario 1: Multiple VLANs configured
Scenario 2: No VLANs/Default Cisco VLAN 1 configured
Scenario 3: One VLAN configured
Troubleshooting

Note: The VLAN and Interface IDs in the configuration provided below are only examples to assist in visualising what's required.

Scenario 1: Multiple VLANs Configured

!

vlan 200-206

!

interface FastEthernet0/37

end

!

!

interface FastEthernet0/47

switchport trunk allowed vlan 200-206

switchport mode trunk

end

!

monitor session 2 source interface Fa0/47

monitor session 2 destination interface Fa0/37

!

Scenario 2: No VLANs/Default Cisco VLAN 1 Configured

!

!

interface FastEthernet0/37

end

!

!

interface FastEthernet0/47

end

!

monitor session 2 source interface Fa0/47

monitor session 2 destination interface Fa0/37

!

Scenario 3: One VLAN Configured

!

vlan 200 (1-4094)

!

interface FastEthernet0/37

end

!

!

interface FastEthernet0/47

switchport access vlan 200

switchport mode access

end

!

monitor session 2 source interface Fa0/47

monitor session 2 destination interface Fa0/37

!

Troubleshooting Command

show monitor session 2 detail

!

See Also
To see how to setup Sinefa to receive span / mirror traffic see How to Setup Span and Mirror Port monitoring

More information on SPAN is available on the Cisco site