Third-party backup software fails to back up VMs via HotAdd transport

Products

• VMware vCenter Server

Issue/Introduction

• Third-party backup software fails to perform virtual machine backups using the HotAdd transport mode through vCenter Server.
• For more information about HotAdd, see HotAdd Transport.
• The backup vendor’s investigation confirmed that vCenter fails to return the VMDK metadata required by VixDiskLib. As a result, VixDiskLib cannot retrieve the disk UUID, causing HotAdd mounting to fail.
• In the vCenter /var/log/vmware/vpxd/vpxd.log:
  
  [YYYY-MM-DDTHH:MM:SS] error vpxd[#####] [Originator@6876 sub=HTTP server /folder] Nfc_EstablishAuthdConnectionEx: returned false, errMsg: Failed to connect to server <ESXi_FQDN>:902

Environment

VMware vCenter Server 8.x

VMware vSphere ESXi 8.x

Cause

TCP port 902 between vCenter Server and the ESXi hosts is blocked by the network device.

Verify the 902 port connectivity from vCenter via SSH：

nc -zv <ESXi_IP> 902

Resolution

To resolve the backup failure, ensure that TCP port 902 is open between vCenter Server and all ESXi hosts.

For more infomation about vSphere port requirement, see VMware Ports and Protocols.