It seems that HP are getting around to fixing the issue of duplicate Cisco Nexus nodes being discovered (it’s not in patch 5) but until then, it’s possible to work around this. Duplicate discoveries play havoc with RRG alerting which isn’t funny when someone’s woken up in the middle of the night for it.
To stop NNMi discovering duplicate nodes once you have the devices in your topology, do the following:
1) Create an Auto-Discovery rule with the lowest ordering in the list (eg: No-AutoDiscover-Rule)
2) Uncheck all options on the left hand pane and uncheck Enable Ping Sweep
3) Add the IP addresses of all the mgmt0 interfaces in the management VRF (Type: Include in rule)