Solved: VMware ESXi Host Not Responding in vCenter

Symptoms: VMware Host Not Responding in vCenter

It’s believed that most VMware administrators have experienced VMware ESXi hosts were showing as "not responding" in vCenter Server. The specific symptoms are:

• ESXi host shows as "not responding" in vCenter Server.
• ESXi host shows as "disconnected" in vCenter Server.
• Cannot connect ESXi/ESX to vCenter Server.
• Virtual machines on the ESXi host shows as grayed out in vCenter Server.
• When attempting to add an ESXi/ESX host to vCenter Server, you see an error similar to:

"Unable to access the specified host, either it doesn't exist, the server software is not responding, or there is a network problem."

This article covers the process of troubleshooting an ESXi host that is in a disconnected or a not responding state in vCenter Server. It guides you to eliminate common causes for your problem by verifying that the configuration of your networking and management server agents is correct, as well as confirming the availability of resources on your ESXi host.

How to Fix ESXi Host Not Responding Error in vCenter

There are many reasons for ESXi host in a disconnected state. So today's article will offer you steps to troubleshoot an ESXi host "not responding" in vCenter Server.

✍ After each step, try to connect to vCenter Server. Do not skip a step.

1. Verify that the ESXi host is in a powered-on/off state

First of all, the easiest way is to check the current state of the ESXi host hardware, or whether the power supply unit has reached its battery life, after which the host is simply turned off.

Physically go to the ESXi host hardware, and make note of any lights on the face of the server hardware that may indicate the power or hardware status.

2. Verify that the ESXi host can be reconnected

You could try to reconnect the disconnected ESXi host, and see if reconnecting the ESXi host resolves the issue.

Just right-click the host and select Summary >> Connection >> Connect.

3. Verify that the ESXi host is able to respond back to vCenter Server at the correct IP address

You need to check if you have network connectivity from vCenter Server to the ESXi host with the IP and fully qualified domain name (FQDN). The steps are to connect to your vCenter Server Windows box first, then open a command prompt where you can check whether you can ping your ESXi host via IP address and FQDN.

If you're running vCenter Server Appliance (VCSA) on Photon OS Linux, you can simply open a terminal to the Linux command shell and do a ping command via the IP address and FQDN.

If you don't see a reply, you can look at your DNS server to see if you have any problems with the DNS resolver.

4. Verify that you can connect from vCenter Server to the ESXi host on TCP/UDP port 902

It may be necessary to test connectivity to the different ports on your servers. The server uses this port for host access to other hosts for migration and provisioning, for authentication traffic for ESXi, and for remote console traffic (xinetd/vmware-authd).

You could use Telnet for vSphere Client access to VM consoles or for a (UDP) status update (heartbeat) connection from ESXi to vCenter Server. In the command prompt window, enter this:

☛ server: the hostname or IP address of the server.
☛ port: the port you want to connect to.

5. Restart Management Network

This service is responsible for synchronizing VMware components and granting access to the ESXi host through the vCenter Server. For detailed information, you could check out the VMware knowledge base (KB) article about Restarting the management agents in ESXi.

6. Check if the VPXA agent has stopped responding on the affected ESXi host

The vCenter Server agent, also known as "vpxa" or the "vmware-vpxa" service, is what allows a vCenter Server to connect to an ESXi host.

The vpxa agent is responsible for communication with the hostd agent, which in turn communicates with the ESXi host. If the vpxa agent has stopped responding on the affected ESXi host, vCenter Server is unable to contact this host, and as such, the host appears as grayed out in the vSphere Client.

To see this, you could connect directly to the ESXi host and try to enter this command:

7. Troubleshooting underlying storage issues

Let’s assume that you’ve already checked everything else, and it didn’t help you out. Well, now the only thing left to do is checking the storage issues on your ESXi host.

ESXi hosts can disconnect from vCenter Server due to underlying storage issues. This could be a shared storage problem, and in this case, you might experience multiple hosts in a disconnect status.

It might also be a failed network interface card (NIC), which, due to a problem, fails to maintain connectivity to the vCenter Server system.

You might experience some of these symptoms:

• Connectivity issues to the storage array
• ESXi host initiators are not logging into the array
• The ESXi host cannot mount the share

Storage issues can be multiple due the fact that you might be using different storage protocols like iSCSI, NFS, or SAN.

The issue of ESXi host not responding in vCenter may appear on multiple VMware hosts. It’s necessary to backup VMware ESXi VMs to avoid the data loss due to reversible tasks.

Backup solution to prevent virtual machine crashes

vCenter Server is a very convenient official platform for centrally managing ESXi virtual environments and large numbers of VMs on it. A single vCenter Server instance can support a maximum of 1,000 hosts, 10,000 powered-on virtual machines and 15,000 registered virtual machines.

However, vCenter Server does not provide the feature of virtual machine backup. And that makes backup software a commonly accepted choice. A professional backup tool is more efficient than the built-in features.

Here I introduce you to a VMware backup software -- AOMEI Cyber Backup. It automates the backup process of multiple VMs managed by vCenter Server, and sends email notifications if there's an error.

✦ Agentless Backup: create complete and independent image-level backup for VMware ESXi and Hyper-V VMs.
✦ Multiple VM Backup: batch backup large numbers of VMs managed by vCenter Server, or multiple VMs on a standalone ESXi host.
✦ Multiple Storage Destinations: backup to local or network share destinations.
✦ Automated Execution: create backup schedules to automate backups daily, weekly, or monthly.
✦ Restore Entire VM: restore immediately available VMs from any selected restore points.

AOMEI Cyber Backup supports VMware ESXi 6.0 and later versions. You can click the following button to download the 30-day free trial.

4 Steps to batch backup VMs on vCenter Server

1. Bind Devices: Access to AOMEI Cyber Backup web client, navigate to Source Device > VMware > + Add VMware Device to Add vCenter or Standalone ESXi host. And then click … > Bind Device.

2. Create Backup Task: Navigate to Backup Task > + Create New Task, and select VMware ESXi Backup as the Backup Type.

3. Set Task Name, Device, Target, Schedule, and Cleanup as needed.

• Task Name: you can change the task name or use the default name with an ordinal.
• Device: batch select large numbers of VMs managed by vCenter Server for centralized backup.
• Target: select to back up to a local path, or to a network path.
• Schedule (optional): perform full, differential, or incremental backup, and automate execution according to the frequency you specified.

• Cleanup (optional): automatically delete the old backup copies that exceed the retention period you specified.

4. Run Backup: Click Start Backup and select Add the schedule and start backup now, or Add the schedule only.

✍ Created backup tasks will be listed and monitored separately, for progress checking, schedule changing and restoring. It’s easy to restore a virtual machine in the same or another datastore/host, without reinstalling or configuring a new VM by clicking Restore to new location.

Summary

When your ESXi host is in disconnected or grayed-out state, you could see that VMware ESXi hosts were showing as "not responding" in vCenter Server.

This article offers efficient steps to troubleshoot a VMware ESXi host is in not responding state. You could verify if your host is powered on, initiate ping tests to both sides (port 902), restart Management agents, or reconnect your host to vCenter inventory. Furthermore, such as checking if the vpxa agent or hostd service is up and running. In the end, see if there are storage problems.