PRP LAN A/B duplicate drop counter check on IvS

Products

• VMware NSX

Issue/Introduction

Industrial vSwitch (IvS) can provide network redundancy for industrial ethernet called Profinet by using Parallel Redundancy Protocol (PRP). PRP Dual Attached Node (DAN) and Redundancy Box (RedBox) have two connections for LAN A and LAN B networks and forward the same frames to both netwokrs after duplicating. IvS recieves the duplicated frame on both LAN A and LAN B, then use the frame that arrived first and discard the second one. 

The question is how to determin which network is selected more, LAN A or LAN B.

Environment

4.2.x

Resolution

The output of the PRP node list has a field called DupDrops. It shows the counter of dropped frames due to duplication. If you look for the MAC address of PRP DAN node in the PRP node list, you can find the DupDrops counter "DupDrops" per LAN A or LAN B. If the DupDrops counter of LAN A is less than LAN B, then means that PRP frames from LAN A are more selected due to LAN A being in better condition than LAN B.

 - Get the MAC address of the NIC that is connected Profinet network
 - Login to the ESXi Host via SSH
 - Run the command and find the DvsPortset name for the MAC address

net-stats -l

 - Run the command and find Switch ID (swID) for the DvsPortset

nsxcli -c get ens switch list

 - Run the command and find the entry for the MAC address in the node table output

nsxcli -c get ens prp stats node <swID>

 - Check the DupDrops counters for LAN A and LAN B