VUM scan fails with error "VMware vSphere Update Manager had an unknown error. Check the events and log files for details"

Products

• VMware vCenter Server
• VMware vSphere ESXi

Issue/Introduction

Symptoms:

• Scanning an ESXi host  fails with error "VMware vSphere Update Manager had an unknown error. Check the events and log files for details"
• vmware-vum-server.log on the VUM server  shows the below errors:
  • [<YYYY-MM-DD>T<time>'SingleHostUpgradeScanTask.SingleHostUpgradeScanTask{321}' 139906224486144 ERROR] [singleHostUpgradeScanTask, 277] Error while scanning: Connection refused: The remote service is not running, OR is overloaded, OR a firewall is rejecting connections.
• vmware-vum-server.log on the VUM server  shows the below errors:
  • <YYYY-MM-DD>T<time> warning vmware-vum-server[23811] [Originator@6876 sub=Default] Failed to connect socket; <io_obj p:0x00007f3e20026fd0, h:25, <TCP '<IP of VUM server> : 37082'>, <TCP '<IP of ESXi host> : 80'>>, e: 111(Connection refused)
• Running nc (netcat) command on the ESXi host port 80 fails with connection refused error:
  • nc -z <destination-ip> <destination-port>
    
    • Example nc -z 192.xx.xx.xxx 80
Connection to 192.xx.xx.xxx 80 port [tcp/http] Connection refused!

Cause

VUM requires port 80 to be open between the VUM/vCenter server and the ESXi host. If a Firewall is blocking port 80, then you see these errors.

Resolution

Open port 80 on the Network Firewall between VUM/vCenter and ESXi hosts

Additional Information

Troubleshooting network and TCP/UDP port connectivity issues on Hosts