vSphere Replication Configuration Fails with Error 503: Unable to Establish TCP Connection Due to Hostname Misconfiguration
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vSphere Replication Configuration Fails with Error 503: Unable to Establish TCP Connection Due to Hostname Misconfiguration

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Article ID: 401264

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Updated On:

Products

VMware vSphere ESXi

Issue/Introduction

Symptoms

When configuring vSphere Replication, the following issues and errors are observed:

  • Not all host-based replication servers appear in the Replication Servers tab within the vSphere Replication UI.

  • Repeated task failures in the vCenter Server client with the error: Config vSphere Replication failed with the following error: cannot establish TCP connection, unexpected status code: 503

  • vSphere Replication Management Server (VRMS) appliance was freshly deployed and registered successfully with vCenter and the cluster.

  • Configuration tasks fail with HTTP Error 503 (Service Unavailable):   Unexpected status code: 503

Network Verification:

  • Ports 443 and 31031 confirmed open between VRMS and ESXi hosts.

  • Ping and connectivity validated after network team verification.

Environment

VMware vSphere Replication 9.x
VMware vSphere Replication 8.x

Cause

This issue occurs when hostname configuration for the vCenter Server and ESXi hosts is incorrect. Specifically:

  • vCenter Server and ESXi hosts were configured with the hostname localhost, instead of valid Fully Qualified Domain Names (FQDNs).
  • As a result, the VRMS appliance fails to resolve and establish communication with the required services, leading to the 503 errors during configuration.
Log Snippets
  • From the /var/log/vmware/vsphere-ui/vsphere_client_virgo.log on vCenter:

[2025-06-11T09:40:13.396+07:00] [ERROR] sdk-plugin-deployer-14023     com.vmware.vise.plugin.download.PluginDownloadServiceImpl         Downloading plug-in package 'com.vmware.drui.plugin:9.0.2.24401761' to
 '/etc/vmware/vsphere-ui/vc-packages/vsphere-client-serenity/com.vmware.drui.plugin-9.0.2.24401761/plugin-package.tmp' has failed due to unknown reasons. Removing failed plugin package folder '/etc/vmware/v
sphere-ui/vc-packages/vsphere-client-serenity/com.vmware.drui.plugin-9.0.2.24401761'. java.net.UnknownHostException: replication.appliance: Temporary failure in name resolution

  • From /opt/vmware/hms/logs/hms.log on the VRMS appliance:
    • The system attempted to enable replication traffic on this host using a NIC (vmk2) with only link-local IPs, but could not establish communication.

2025-06-11 12:02:33.433 ERROR com.vmware.hms.monitor.hostEnableHostAtHbrTaskRunner [hms-config-host-at-hbr-thread-1] (..monitor.host.EnableHostOnHbrHelper) [operationID=########-####-####-####-############-HMSINT-8] | Failed to enable host##.##.##.##(host-##) for addresses [##.##.##.##, ####::####:####:####:####], using NICs [vSphereReplicationNFC.key-vim.host.VirtualNic-vmk2].
2025-06-11 12:02:33.433 ERROR com.vmware.hms.monitor.hostEnableHostAtHbrTaskRunner [hms-config-host-at-hbr-thread-1] (..jvsl.util.Slf4jUtil) [operationID=########-####-####-####-############-HMSINT-8] | Failed to enable host##.##.##.##(host-##) on any NIC in VR server replication.appliance(########-####-####-####-############).
2025-06-11 12:02:33.433 ERROR com.vmware.hms.monitor.hostEnableHostAtHbrTaskRunner [hms-config-host-at-hbr-thread-1] (..host.task.EnableHostAtHbrTaskRunner) [operationID=########-####-####-####-############-HMSINT-8] | Error while enabling host host-## in VR Server ##.##.##.##

    • HMS is trying to register the vSphere Replication server module on host, however the registration is getting failed

2025-06-11 12:02:38.599 ERROR com.vmware.hms.remote.SiteManager [hms-main-thread-8] (..hms.remote.SiteManagerImpl) [operationID=########-####-####-####-############-HMSINT-8, task=HTID-########-####-####-####-############] | Unable to register VR Server vm '##.##.##.##' uri 'https://##.##.##.##:443/hbr' thumbprint '##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##:##'

    • The service hbrsrvuw on the host is not registering with HMS, which is needed for replication to work.

2025-06-11 12:02:38.602 ERROR com.vmware.hms.hbrsrvuw.HbrsrvuwRegistrarService [hms-main-thread-2] (..hms.hbrsrvuw.HbrsrvuwRegistrarService$HostTask) [operationID=########-####-####-####-############-HMSINT-8] | Register hbrsrvuw from host-##...FAILED (HTID-########-####-####-####-############); will retry

    • HMS is periodically pinging the HBR service on the host to check health and connectivity, however the ping is getting failed

2025-06-11 12:02:38.607 ERROR com.vmware.hms.net.hbr.ping.svr.########-####-####-####-############ [hms-ping-scheduled-thread-3] (..net.impl.VmomiPingConnectionHandler) [operationID=########-####-####-####-############-HMSINT-8, operationID=########-####-####-####-############-HMS-PING] | Ping for server##.##.##.##:443/hbr for session: N/A failed:

Resolution

Workaround

  • Update Hostnames to Use FQDNs

    • Rename the vCenter Server to use a valid FQDN.
    • Rename all ESXi hosts to use valid FQDNs (avoid using localhost or short names).

  • Renew Certificates

    • After renaming, renew the SSL certificates for both vCenter Server and all ESXi hosts.

  • Reconfigure vSphere Replication

    • Reconfigure the vSphere Replication appliance.
    • Use the PSC FQDN during configuration.
    • Ensure the vSphere Replication appliance’s FQDN is resolvable in DNS.
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