ESXi 5.x and 6.0 hostd.log continuously displays error: "Network memory pool free size dropped below # percent"

Products

• VMware vSphere ESXi

Issue/Introduction

• The vSphere Client connected either directly to the host or to vCenter Server displays this event every 5 seconds:
  
  Network memory pool free size dropped below 2 percent
   
• In the /var/log/hostd.log file, you see entries similar to:
  
  [54A08B90 info 'ha-eventmgr'] Event 6428 : Network memory pool free size dropped below 2 percent.
  Section for VMware ESX, pid=785831, version=5.1.0, build=914609, option=Release
  
  [54A08B90 verbose 'SoapAdapter'] Responded to service state request
  
  [52860B90 info 'VmkVprobSource'] VmkVprobSource::Post event: (vim.event.EventEx) {
  
  --> dynamicType = <unset>,
  --> key = 11,
  --> chainId = 20,
  --> createdTime = "1970-01-01T00:00:00Z",
  --> userName = "",

Cause

The ESXi host runs a task that checks the netPktPool memory usage every 5 seconds. When the available memory is below the threshold value the alarm is triggered when the task runs, creating the messages in the hostd.log file and the events displayed in vCenter Server. This continues until the available memory is above the threshold value for the netPktPool. This can appear when there is a burst in network traffic and there are unused buffers in the pool that have not been cleared.

Resolution

This issue is resolved in:

• VMware ESXi 5.1 Patch Release ESXi510-201510401.
• VMware ESXi 5.5 Patch Release ESXi550-201512001.
• VMware ESXi 6.0 Update 1.

This issue does not affect the performance of the host.

To work around this issue, use one of these options:

• Reduce any non-iSCSI vSwitches from Jumbo Frame (9000) to default (1500). This can prevent or delay the re-occurrence of the warning depending on the network traffic.
• Rebooting the host resolves this issue temporarily.