I recently added netflow to our nexus 7k and getting these messages. I know they refer to our vlans on the nexus and I am currently monitoring those vlans. I have seen reports about using the snmp-server ifindex persist command but when I try to issue the command the nexus doesn't like it. looking at the command options ifindex is not one of them. Any suggestions.
|NetFlow Receiver Service [SW] is receiving flow data from unmanaged interface '#8' on nexus and it does not support SNMP. Click the "Add this interface" to manage interface and process its flow data.|
Just realized that NX-OS has ifindex persistence enabled by default. But I also happened to find this thread where it says that ifindex can change.
Could it be that you have an older IOS on the device? And can you check the interface name for ifindex8 on the Nexus. I believe the command for NX-OS is "show interface snmp-ifindex". You can check the interface name for ifindex 8 and then check if NPM is managing it or not.