Solved: VMware ESXi Host Not Responding in vCenter

Symptoms: VMware ESXi Host Not Responding in vCenter

Many VMware administrators utilize the VMware vCenter to manage multiple ESXi hosts and VMs. However, you may find that your VMware ESXi hosts were showing as "not responding" in the vCenter Server web interface or can't synchronize the host.

The specific symptoms are:

• ESXi host shows as "not responding" in vCenter Server (when adding IP address, performing an operation, or after an upgrade, etc.)
• Esxi host not responding but VMs still running
• 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."

Common reasons for a host get not responding status: 

• A network connectivity problem between the ESXi host and vCenter.
• hostd agent is not working properly.
• vpxa is not working properly.
• The ESXi has failed.

It is not a rare problem, many administrators have experienced this issue. You can keep on reading. This article covers the process of troubleshooting an ESXi host in a disconnected or 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

In this part, we will offer your steps to troubleshoot the "vCenter host not responding" issue. You can try the following troubleshooting steps one by one, please don't skip a step.

✍ Please be careful when you dealing with the problem.  An accidental operation can impact tasks running on your VMs. Thus, please backup your virtual machines in vCenter beforehand to ensure your VM data security and business continuity.

Step 1. Check if the ESXi host is powered on

First, 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.

Step 2. Reconnect the ESXi host

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

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

 

Step 3. Verify the host connectivity to vCenter at the right IP address

If there is a connectivity problem from vCenter to ESXi host with the IP and fully qualified domain name (FQDN), vCenter Server does not receive heartbeats from the ESXi host and causes the host not to respond and disconnected issue.

To verify that your ESXi host can respond back to the vCenter Server at the correct IP address and FQDN, you can pin the host IP address and check the DNS service:

How to ping your ESXi host via IP address and FQDN: 

• Press Windows key + R to run Windows box, and types cmd and press Enter to open Command Prompt.

• Run command "ping ". Replace with your actual IP address of the host.

• To ping the host by its FQDN, run command "ping ". Replace the with your actual FQND name.

If the ping is successful, you'll receive a response from the host, showing round-trip times and packet statistics. If the ping fails, you can look at your DNS server and see if you have any problems with the DNS resolver.

How to verify DNS Resolution

•  Run the command "nslookup  ". Replace vCenter _FQDN with the fully qualified domain name (FQDN) of your vCenter Server.

If the DNS resolution has an issue, check and make sure your DNS is properly configured.

If your ESXi host disconnected or not responding but is able to ping, You can refer to the next step.

Step 4. Verify the vCenter Server can connect to the 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.

If you see the output:

C:\>telnet server 902
Connecting...

The connection is working, If you see an error "Could not open connection to the host, on port 902: Connect failed", it means the connection is refused. This could be the real reason why the host is not responding, you can keep on reading to troubleshoot it.

Step 5. Restart Management Network

Management network synchronizes VMware components and facilitates communication between ESXi host and vCenter Server. If vCenter cannot synchronize host or cannot directly connect to the ESXi host, you can restart the Management Network.

To restart the Management Network on ESXi:

1. Connect to the ESXi host console. 

2. Press F2 to configure the system. 

3. log in as root and navigate to Restart Management Network using the up and down arrow keys.

4. Press Enter to restart the Management Network.

Step 6. Check if the VPXA agent is not responding on the  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:

Step 7. Troubleshooting underlying storage issues

Let’s assume you’ve already checked everything else, and it didn’t help you. Well, now the only thing left to do is check 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 because 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, external storage, network share, NAS drive 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.
• Archive (optional): If you have an Amazon S3 storage, you can archive backup versions to it.
• 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 not responding in vCenter or in a disconnected, greyed-out state and the VMs , you can follow the troubleshooting steps provided in this article. 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.

In addition, don't forget to back up your VMware ESXi virtual machines in case of an accident. AOMEI Cyber Backup is a robust and easy-to-use enterprise backup solution that enables you to easily protect your virtualized environment, as well as other workloads, like Windows computers, and MSSQL databases.