Checking and Monitoring Network Packet Drops on ESXi Hosts via CLI

Products

• VMware vSphere ESXi

Issue/Introduction

Third-party monitoring software (such as Dynatrace) may report ESXi network problems indicating dropped packets on specific hosts. For example, you might see an alert similar to: "Dropped 179 packets/sec on network interface vmnic# of ESXi Host ###########". Administrators require a reliable method to verify, check, and actively monitor these dropped packet statistics directly on the ESXi host to confirm the alerts and begin troubleshooting.

Environment

VMware vSphere ESXi (All supported versions)

Resolution

The most accurate way to retrieve exact statistics on packet drops for physical network interfaces (vmnics) is through the ESXi CLI.

1. To check current packet drop statistics:
   
   
   1. Connect to the affected ESXi host via SSH using the root account.
      
      
   2. Run the following command to get the network statistics for the specific interface (replace vmnic# with your affected interface name):
      
      esxcli network nic stats get -n vmnic#
      
      
   3. In the command output, locate the following fields to review your drop counts:
      
      Receive packets dropped
      
      Transmit packets dropped
      
      
2. To monitor packet drops in real-time:
   
   
   1. If you want to monitor active increments in packet drops while troubleshooting, use the watch command. From the same SSH session, execute the following command:
      
      watch -d esxcli network nic stats get -n vmnic#
      
      This will display incremental values, refreshing the screen every 2 seconds. The -d (differences) flag will highlight any values that change between updates, allowing you to easily see if packets are actively dropping.
      
      
   2. Press Ctrl+C to exit the watch command and return to the prompt.

Additional Information

• Counter Resets: Please note that the "Receive packets dropped" and "Transmit packets dropped" numbers reflect the total packets dropped since the last reboot of the ESXi host. They do not reset automatically unless the host is restarted, or unless the counter is manually reset.

• Impact Analysis: To understand the actual impact of the drops, compare the dropped values against the total "Packets received" and "Packets sent" metrics found in the same output. This comparison will tell you what percentage of the total packets handled by the vmnic are actually being dropped.