Possible redundant netflow configuration

[dan0923]

We are receiving flow data on all devices. We have GRE tunnels connecting remote sites to our data center. Some of these sites have flow configuration on both the physical interface on our routers as well as our tunnels, and some have the flow configuration solely on our tunnels. However, we are receiving flow data from all sources. 

The following white page states that "Before it can be activated, a flow monitor must be applied to at least one interface". I was wondering if the tunnel interface is enough to fill that requirement, and we have redundant statements on our physical ints? 

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/fnetflow/configuration/15-mt/fnf-15-mt-book/fnf-l2-fields.html

Thank you. 

[balaji.bandi]

Depend on where you want to collect Flows.

if the tunnel interface is the edge where you see all the traffic, then yes that is the interface you need to enable flows to collect for better understand flows in the network.

[dan0923]

Thank you for taking the time to respond. 

Yes, the tunnel is on the edge of our spoke sites pointing back to our data center. Does that mean we would need a the config on either the tunnel or the physical int, and not necessarily both?

Thank you again .