"TTL 1 is not greater than VDR action data hops" Flow Cache messages spam ESXi vmkwarning log

Products

• VMware NSX

Issue/Introduction

• ESXi host logs are flooded with log entries similar to the below:
  /var/run/log/vmkwarning.log
  

  <Timestamp> Wa(180) vmkwarning: cpu64:2098149)WARNING: FlowCache.fc: FC_ActionVDR:1419: [nsx@6876 comp="nsx-esx" errorCode="ESX6"]TTL 1 is not greater than VDR action data hops 1

• There is no dataplane traffic impact observed for the VM traffic hosted on the ESXi host.

Environment

VMware NSX

Cause

Decrementing TTL is expected logic in Layer 3 networking.  When TTL is decremented to zero for a packet, then that packet gets dropped.  Applications can also purposefully set packets with a low TTL value.

Resolution

This issue is resolved in VMware NSX 4.1.1, available at Broadcom downloads.
From NSX 4.1.1, the process is optimized by replacing these logs with counters on flow-cache stats which can be observed with the following host command:
nsxdp-cli fc stats get

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