AC 800M PM851 controller is randomly disconnecting From RNRP.
PM851 controller is getting down from RNRP, But continously pinging from Connectivity server. I had confirmed that there is no duplicate IP in this network.
Voted best answer
What are your IP addresses?
RNRP will only start automatically if you use 172.x.x.x addresses (so called Implicit Addressing method).
With other addresses you must manually configure RNRP (so called Explicit Addressing method).
Please read about RNRP parameterization in the Automation System Network User's Guide, 3BSE034463-600.
The RNRP Fault tracer can be used to probe a controller with RNRP status down. If the controller answer, RNRP is probably running, but RNRP telegrams are blocked, e.g. in the switches.
The above user's guide also states what is required from the network, e.g. free multicasting must be enabled in the switches. Often, this mean that you must turn OFF features like IGMP Snooping and Ageing.
E.g. Cisco and Westermo switches have this ON in factory default.
Some switches, e.g. Cisco require a dedicated programming tool to allow adjusting these features, e.g. Cisco CLI or Cisco Network Assistant.
Since you write random disconnections I would assume RNRP is running and the switches allow multicast; but IGMP Ageging can strike after some delay. Please have all items checked.
It might be for the best if you seek professional help from your regional ABB support center. They can escalate cases to our Center of Excellence.