Host shows the vSphere HA status as Network Partitioned due to network problems

Products

• VMware vSphere ESXi

Issue/Introduction

• A host reports the vSphere HA status as Network Partitioned.
• The host cannot reach the vCenter server.
• The host cannot reach other hosts in the cluster.
• While running ICMP ping tests, packet captures were done on the ESXi using "Pktcap-uw" commands. (Please see KB: Packet capture on ESXi using the pktcap-uw tool for guidance on how to take packet captures on ESXi)
• These packet-captures show that icmp requests can be seen on the VMNICs of the problematic host, but the same requests cannot be seen on any of the VMNICs of the other hosts, or the host where the vCenter VM resides.

Environment

• VMware vSphere 8.x
• VMware vSphere 7.x
• VMware ESXi
• VMware vCenter Server

Cause

When performing an ICMP ping test, if packet captures reveal that ICMP requests are transmitted from the source host's VMNICs but are not received by the destination host's VMNICs, this suggests that the packets are being dropped within the underlay or physical network infrastructure.

The physical network dropping these communications is leading to vSphere HA showing as Network Partitioned. This is because for vSphere HA to work properly, an ESXi participating in the HA should be able to communicate with other ESXis in the cluster and also with the vCenter. Please see vSphere HA Checklist for reference.

Resolution

Please engage with the internal network team to investigate the physical layer of the network path and identify the point at which packets are being dropped. Engaging the firewall management team may be necessary too if firewalls are in the network path.

Additional Information

When a host reports vSphere HA Network Partitioned, but all hosts and the vCenter have confirmed network reachability, then the root cause may be different. You can look into this KB: Host shows the vSphere HA status as Network Partitioned