Cisco Catalyst SPAN and Remote SPAN Configuration

To analyze network traffic passing through ports or VLANs you can configure SPAN or remote SPAN to mirror the traffic to another port on the switch or on another switch that has been connected to a network analyzer. The network analyzer can be Wireshark or Riverbed Cascade Pilot what capture or analyze the traffic. Cascade Pilot is here quite interesting because you can filter the traffic before and then send it to Wireshark for a deep analysis.

Back to the configuration, SPAN mirrors traffic received or sent (or both) on source ports or source VLANs to a destination port for analysis. The SPAN session does not affect the switching of network traffic on the source. Except for traffic on the destination, ports do not receive or forward traffic there are shown as monitoring interfaces.


Configure local SPAN session:

Define the source interface which traffic you want to mirror

monitor session 1 source interface GigabitEthernet 0/41

or VLAN as source

monitor session 1 source vlan 500

Define the destination interface

monitor session 1 destination interface GigabitEthernet 0/10


Configure remote SPAN session (1st switch):

At first create an remote SPAN VLAN

vlan 2010

Then like the local SPAN session define the source

monitor session 1 source interface gi 0/47


monitor session 1 source vlan 500

At the end of the configuration of the 1st switch you configure the remote SPAN VLAN as destination

monitor session 1 destination remote vlan 2010


Configure remote SPAN session (2nd switch):

Like on the other switch you need to create at first an remote SPAN VLAN

vlan 2010

Then as source you configure the RSPAN VLAN

monitor session 1 source remote vlan 2010

In the end the destination interface

monitor session 1 destination interface gi 0/18

Important is to verify that the RSPAN VLAN is allowed between these two switches on thier Trunk Interfaces!


With the following command you can verify the monitoring session you configured

show monitor session 1

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