VMs experience intermittent ping loss and network drops from ESXi host

Products

• VMware vSphere ESXi

Issue/Introduction

• VMs experience intermittent network connectivity drops and lose pings even between VM's of same ESXi and same port group when an uplink is connected to the vswitch but when there are no uplinks attached to the vswitch, the VM's communicate fine with no ping drops.
• The issue persists even after rebooting or migrating the affected VMs.
• Packet captures indicate that ICMP requests reach the destination VM, but the destination VM intermittently responds to an incorrect MAC address, leading to packet drops.

Environment

VMware vSphere ESXi

Cause

• These network connectivity drops are caused by an IP address conflict.
• Another virtual machine on the same network is claiming the same IP address as the affected VM, causing ARP confusion and forcing the destination to respond to the conflicting machine's MAC address instead of the correct original MAC address.

Resolution

To verify and resolve the IP conflict:

1. Power off the affected VM experiencing the network drops.

2. From another machine on the same network, attempt to ping the IP address of the powered-off VM.

3. If the IP address responds to the ping while the original VM is off, an IP conflict is confirmed.

4. Identify the conflicting machine claiming the duplicate IP address.

5. Power off or reconfigure the network settings of the conflicting machine to ensure the IP address is uniquely assigned.

6. Power the original affected VM back on and verify that network connectivity is fully restored.