The host appears as disconnected in vCenter

Products

• VMware vSphere ESXi

Issue/Introduction

The host appears as 'Disconnected' in vCenter, and when attempting to reconnect, an error message is displayed.: "Cannot contact the specified host hostname\IP. The host may not be available on the network, a network configuration problem may exist, or the management services on this host may not be responding"

Environment

VMware ESXi 7.x
VMware ESXi 8.x

Cause

The error message is caused by a network misconfiguration at the host level, which may involve incorrect network settings, such as IP address, subnet mask, gateway, or VLAN configuration. This misconfiguration prevents proper communication between the host and other network components, leading to connectivity issues and triggering the error.

Resolution

To fix the issue, validate the below settings:

Solution 1:

• Verify if the host is pingable and ensure the NIC card is functioning properly.
• If there is an issue with NIC, isolate it by disabling the active NIC and testing the traffic using the standby NIC.

Solution 2:

• Verify DNS connectivity and if DNS  is not functioning correctly.
• Update DNS server IP on vCenter using the following command:

             /opt/vmware/share/vami/vami_config_net 

Solution 3:

• Validate if the vCenter and host certificates have expired. If they have, update the certificates by referring the below article: Determining expired SSL certificates in vCenter Server and ESXi 6.x and 7.0.x