VCF 9.1.0 deployment fails on "Discover the existing domain from vCenter"

Products

• VMware SDDC Manager / VCF Installer

Issue/Introduction

• VCF 9.1.0 deployment with existing vCenter Server fails on the task "Discover the existing domain from vCenter"
  
  An error occurred in task "Discover the existing domain from vCenter". See Tasks panel to learn more.
  
  
• The /var/log/vmware/vcf/domainmanager/domainmanager.log in SDDC Manager has below similar messages:
  
  2026-06-23T08:12:15.253+0000 ERROR [vcf_dm,6a3a3fba35218134c216a4c832896509,315e] [c.v.v.d.utils.DomainDiscoveryUtil,dm-exec-70]  Exception occurred during domain discovery for vCenter <vcenter-fqdn>
java.lang.IllegalStateException: Fail to fetch appliance info 0: null.
...
Caused by: java.net.SocketException: Socket closed
...
  
  
• The SDDC Manager has been configured with multiple DNS servers.

Environment

VMware Cloud Foundation 9.1.0

Cause

The issue is caused by one of the DNS servers is not working and causing /v1/system/appliance-info to return result for 15 seconds which eventually hits client timeouts in the domainmanager service. The issue is also seen in the validation that reverse DNS lookup has failed.

Resolution

Remove the bad DNS server from SDDC Manager with the steps in VCF deployment with existing vCenter Server fails with error "Specified release version 9.1.0.0 is not compatible with the supported versions ()"

Additional Information

Configure/Update DNS Server IP Address in SDDC Manager or the VCF Installer through Command Line