Further to this, when I drill into the other ports that we haven't set netflow on we don't see any data....
each flow carries information about 2 interfaces - input and output. By default NTA has 'Enable automatic addition of NetFlow sources' option turned ON, that's why some interfaces were added automatically (you should see appropriate messages on Last 25 events resource).
If you don't want this interfaces to be automatically added to NTA monitoring, please navigate to Admin -> NetFlow Settings and check this settings:
- Enable automatic addition of NetFlow sources - OFF
- Allow monitoring of flows from unmanaged interfaces - ON
Thank you Georgiy!