### Understand the alert

This alert is generated when the number of outbound `packets dropped` on a network interface of a `vSphere Virtual Machine` exceeds a specified threshold in the last 10 minutes. Packet drops are an indication of network congestion or misconfiguration, and can cause degraded performance and application slowdowns.

### Troubleshoot the alert

1. Identify the Virtual Machine (VM) and network interface experiencing the issue:
   
   Use the details in the alert to find the Virtual Machine and network interface that triggered the alert. Note the name and location of the VM and the associated network interface.

2. Check for network congestion or misconfiguration:

   Possible reasons for dropped packets can include network congestion, faulty network hardware, or VM configuration issues. Common ways to check for these problems are:

   - Check the performance charts in the vSphere Client for the affected VM, specifically the `Network` section, to visualize the network usage, dropped packets, and other relevant metrics.
   
   - Verify the VM's network adapter settings are correct, such as its speed, duplex settings, and MTU size.
   
   - Check the VM's host machine and its physical network connections for issues, like overutilization or faulty hardware.
   
   - Review any network traffic shaping policies on the vSphere side, such as rate-limiters or Quality of Service (QoS) configurations.
   
   - Examine the VM's guest OS network settings for configuration issues, such as incorrect IP addresses, subnet masks, or gateway settings.

3. Diagnose application or protocol issues:

   If the network settings and hardware appear to be functioning correctly, the dropped packets could be a result of specific application or protocol issues. Inspect the network traffic to see if it's associated with certain applications. In the VM's guest OS, use tools like `tcpdump`, `wireshark`, or `iftop` to capture network packets and check for problematic patterns, or review application logs for any network issues.

4. Address the problem and monitor the situation:

   Once you've identified and addressed the underlying cause of the dropped packets, continue monitoring the VM's network performance to verify that the issue has been resolved. If the alert persists or the problem comes back, consider escalating the issue to the network engineering team or VMware support for further assistance.

### Useful resources

1. [VMware Knowledge Base - Diagnosing Network Performance Issues](https://kb.vmware.com/s/article/1004089)
