ESXi Host Disconnected from vCenter due to Host IP Address Conflict Detected : Quick Fix

Introduction

When you managing VMware vSphere, sometimes you may see your ESXi hosts marked as Disconnected in vCenter. One of the most common problems VMware administrators face is when an ESXi host gets disconnected from vCenter due to an IP address conflict. This issue not only disrupts connectivity but can also put your virtual environment at risk if not resolved quickly.

In this article, we will explore reason behind the esxi host disconnected due to IP Conflict error showing in host event and quick finding and resolution using log analysis.  

Role of vCenter in VMware Environment

vCenter Server is the centralized management platform for all ESXi hosts. It helps administrators manage clusters, monitor performance, provision VMs, and apply policies and features across multiple hosts. If an ESXi host becomes disconnected from vCenter, managing workloads becomes challenging, and high availability (HA) or distributed resource scheduling (DRS) may fail.

ESXi Host Disconnected

A host is marked as Disconnected when vCenter Server stops managing it. Unlike Not Responding, this state is triggered from the vCenter side.

Typical reasons include:

1. A user manually right-clicks the host and selects Disconnect
2. DNS Issues
3. A user attempts to reconnect a Not Responding host, but the reconnect task fails
4. The host license expires

When a host is disconnected:

• It remains in the vCenter inventory
• vCenter does not receive any updates from it
• vCenter stops monitoring its health until it is reconnected

Impact on HA (High Availability)

vCenter handles disconnected hosts in an HA cluster with caution:

• VMs on disconnected hosts are not counted in admission control checks.
• vCenter assumes those VMs will need to fail over if the host fails. However, since the host’s status is unknown, it cannot be used as a guaranteed failover target.
• HA is disabled on the disconnected host until it is reconnected.
• Once you manually reconnect the host, it becomes fully available again for HA failover and management.

Issue Summary

In a specific cluster ESXi hosts showing as “Disconnected” in your vCenter Server. 

While reconnecting it shows error “Host IP address conflict detected”

In vCenter /var/log/vmware/vpxd/vpxd.log looks like:

Warning vpxd[07289] [Originator@6876 sub=InvtHostCnx
opID=HeartbeatStartHandler-460059d8] Host IP address conflict detected. [vim.HostSystem:hostname.net]
is trying to change IP from hostname.net to xx.xx.xx.xx New IP is already used
by hostname.net

 2025-04-11T07:54:40.478Z info vpxd[07287] [Originator@6876
sub=vpxLro opID=lro-31224504-1ecae696] [VpxLRO] — BEGIN lro-31224504 — — HostDisconnectLRO
— 2025-04-11T07:54:40.488Z warning vpxd[07305] [Originator@6876
sub=IO.Connection opID=lro-31224504-1ecae696] Failed to resolve address;
<resolver p:0x00007f9e9824d110, hostname.net:443‘, next:(null)>, e:
1(Host not found (authoritative)), async: true, duration: 8msec
2025-04-11T07:54:40.488Z warning vpxd[07305] [Originator@6876
sub=HttpConnectionPool-000000 opID=lro-31224504-1ecae696] Failed to get pooled
connection; <cs p:00007f9ea4256220, TCP:s70t0038h.apj.dxccorp.net:443>,
(null), duration: 9msec, N7Vmacore15SystemExceptionE 

(Host not found
(authoritative)) –>

Note : The logs shown may different and not similar 

Affected Products : VMware vSphere ESXi (7.x & 8.x)

If you see this kind of error in vpxd logs, most probably this issue occurs when esxi host added in vCenter with hostname (fqdn) and due to DNS issue not able to resolve name to ip and ip to name and ended up with host disconnected state in vCenter.

Cause:

ESXi host is trying to change its IP address to one that’s already in use however the IP it’s trying to change to is already assigned to itself

vCenter detected that the host “esxihostname.net” is now reporting it’s IP instead of FQDN.

Consequence of the DNS failure. vCenter cannot establish a connection to the host using its FQDN because it can’t find the corresponding IP

This indicates that the vCenter server cannot resolve the hostname to an IP address using its configured DNS name.

As a result, vCenter initiates the process to disconnect the host.

Try following checks to confirm the cause of issue.

Check problematic esxi hosts can access esxi web client with name and ip

From the ESXi Host (SSH)

Try to nslookup and reverse lookup vcenter hostname from esxi (nslookup vcenter name and nslookup vcenter ip)

From the vCenter Server (SSH)

Try to nslookup and reverse lookup impacted esxi host fqdn and ip address

nslookup esxi host FQDN and esxi host IP address

Check if vCenter and problematic ESXi Hosts can resolve name to ip and ip to name

Check if you can ping ESXi Management ip address and fqdn from vCenter

Resolution:

If you can’t resolve the name to ip and ip to name and can’t ping ESXi from vCenter nor able to access esxi web client with FQDN e.g. “https://esxihostfqdn.net”, however you are able to access through IP address. Then this confirms to be the DNS issue, reach out to your DNS team if you don’t manage the DNS servers and check impacted ESXi host A record and PTR record.

Once the DNS entries are fixed try reconnecting the esxi host to the vCenter. It will connect like a charm.

Conclusion

An ESXi Host Disconnected from vCenter due to Host IP Address Conflict Detected can disrupt operations, but with systematic troubleshooting, the issue can be resolved quickly. By verifying network settings, eliminating duplicate IPs, and following best practices, administrators can ensure stable VMware environments and prevent future disruptions.

For additional insights, you can also explore VMware’s official documentation.

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