ESXi reporting Transmit Packet Drops on vCenter/vROPS for VM's connected to an overlay network.

Products

• VMware NSX

Issue/Introduction

• vROPS and vCenter reporting Transmit Packet drops for VM on an overlay Network.
• No impact was observed on the VM as far as performance is concerned.
• No connectivity related issues are observed even though we are seeing TX Packet drops being reported. 

Environment

VMware NSX-T Data Center
VMware NSX

Cause

We are seeing Tx drop counts due to ARP Suppression support.

The overlay stack attempted to reduce ARP packet flooding by responding to ARP requests on behalf of the guest.

As a result, those ARP requests were dropped within the I/O chain itself.

/net/portsets/DvsPortset-0/ports/6710XXXX/> get /net/portsets/DvsPortset-0/ports/6710XXXX/inputStats

---  >  VDL2_INPUT.2210XXXX <vdl2-leaf-in:0x4325b2dXXXXX>
                pktsStarted:7921XXX
                pktsPassed:79174XXX
                pktsDropped:59000 <<<<<<< Filtered 
                pktsFiltered:0
                pktsQueued:0
                pktsFaulted:0
                pktsInjected:0
                pktErrors:0

Resolution

Those drops counter error stats are benign and misleading. We are aware of Tx drop reporting logic error. 

This will be fixed in VCF 9.1