Packet drops observed in vCenter performance UI when net-x redirection is enabled for VMs

Products

• VMware vCenter Server
• VMware vSphere ESXi
• VMware NSX Data Center for vSphere

Issue/Introduction

• Packet drop count increments in vCenter Advance Performance UI for all the Virtual Machines which have net-x redirection enabled
• Drop count becomes zero after disabling net-x redirection

Environment

VMware vCenter Server 7.0.x
VMware vSphere ESXi 7.0.x
VMware NSX Data Center for vSphere 6.4.x

Cause

Packet drop count never increments at VM's DVFilter level. However, vCenter is picking these stats from ESXi net-dvs and considering "pktsFaulted" count in DVFilter IO chain as dropped packets.

port <5541>:

com.vmware.common.port.statistics:
pktsInUnicast = 60377465
bytesInUnicast = 4700693480
pktsInMulticast = 123379
bytesInMulticast = 15409840
pktsInBroadcast = 8761
bytesInBroadcast = 1557435
pktsOutUnicast = 459878312
bytesOutUnicast = 678468274530
pktsOutMulticast = 2541600
bytesOutMulticast = 194405394
pktsOutBroadcast = 3592355
bytesOutBroadcast = 289263554
pktsInDropped = 243628198
pktsOutDropped = 1888527327 ==========> Drop Packets
pktsInException = 0
pktsOutException = 0

get /net/portsets/DvsPortset-3/ports/######/outputStats
io chain stats {

DVFILTER_VNIC_OUT_GUEST <serviceinstance-4:########>
pktsStarted:933882
pktsPassed:933882
pktsDropped:0
pktsFiltered:0
pktsQueued:0
pktsFaulted:544263 <---- pktsFaulted == pktsInjected.
pktsInjected:544263
pktErrors:0

}

"Faulted" refers to packets sent to Slow-Path SVM and "Injected" refers to packets re-injected from Slow-Path SVM. There are no drops if Packets Faulted and Packets Injected are the same. 

Resolution

This issue is resolved in ESXi 7.0 U3

This is a Cosmetic issue and there is no impact because of this.

Additional Information

Impact/Risks:

No impact. This is a Cosmetic issue and there is no impact because of this.

This happens only when we use slot-4 in the IO chain, only punted traffic will be considered as dropped.