Symptoms:

• ESX/ESXi hosts fail to scan in vCenter Update Manager 4.1.x, 5.x, and 6.x with the error:

Host cannot download files from VMware vCenter Update Manager patch store. Check the network connectivity and firewall setup, and check esxupdate logs for details.

• Scan task stalls/fails at 10% in the vCenter Server recent tasks.
• In the C:\ProgramData\VMware\Infrastructure\VMware Update Manager\Logs\vmware-vum-server-log4cpp.log file, you see entries similar to:
  
  'scanHost20' 2676 INFO] [scannerImpl, 191] Ruleset disabled
  'InventoryMonitor' 9000 INFO] [InventoryMonitor, 452] ProcessUpdate, Enter, Update version := 305
  'InventoryMonitor' 9000 WARN] [InventoryMonitor, 748] Unexpected filter: session[52e4d79b-779b-6ec9-face-cbe215d9873a]52324f15-50e9-dbdc-fdf4-1bef6173a9e0
  'HostUpdateDepotManager' 2676 ERROR] [scanHost20, 365] result for host: vsphere.local (entity: host-250432) shows error :
  -----Result Begin (vsphere.local)-----
  <esxupdate-response>
  <version>1.40</version>
  <error errorClass="MetadataDownloadError">
  <errorCode>4</errorCode>
  <errorDesc>Failed to download metadata.</errorDesc>
  <url>http://url.local:9084/vum/repository/hostupdate/csco/csco-VEM-5.0.0-metadata.zip</url>
  <localfile>None</localfile>
  <msg>('http://url.local:9084/vum/repository/hostupdate/csco/csco-VEM-5.0.0-metadata.zip', '/tmp/tmpb7hesK', '[Errno 4] IOError: <urlopen error [Errno -2] Name or service not known>')</msg>
  </error>
  </esxupdate-response>
  -----Result End (vsphere.local)-----
  'HostUpdateDepotManager' 2676 ERROR] [scanHost20, 380] esxupdate download failed.
  'SingleHostScanTask.SingleHostScanTask{55}' 2676 ERROR] [singleHostScanTask, 399] SingleHostScan caught exception: esxupdate download failed. with code: 1
  'SingleHostScanTask.SingleHostScanTask{55}' 2676 ERROR] [vciTaskBase, 556] Task execution has failed: integrity.fault.HostPatchEsxFileDownloadFailure
  'scanHost20' 4688 INFO] [scannerImpl, 191] Ruleset disabled
  'HostUpdateDepotManager' 4688 ERROR] [scanHost20, 348] result for host: host1.domain.com (entity: host-62484) shows error :
  -----Result Begin (host1.domain.com)-----
  <esxupdate-response>
  <version>1.30</version>
  <error errorClass="MetadataDownloadError">
  <errorCode>4</errorCode>
  <errorDesc>Failed to download metadata.</errorDesc>
  <errorDesc>[Errno 4] IOError: <urlopen error (-3, 'Temporary failure in name resolution')></errorDesc>
  <url>http://url2.local:9084/vci/hostupdates/hostupdate/CISCO/metadata/csco-VEM400-4.2.1.1.4.1.0-2.0.1-metadata.zip</url>
  <localfile>/var/cache/esxupdate/metadata4692604695380568561/metadata.zip</localfile>
  <message>[Errno 4] IOError: <urlopen error (-3, 'Temporary failure in name resolution')></message>
  </error>
  </esxupdate-response>
  -----Result End (host1.domain.com)-----
  'HostUpdateDepotManager' 4688 ERROR] [scanHost20, 363] esxupdate download failed.
  'SingleHostScanTask.SingleHostScanTask{195}' 4688 ERROR] [singleHostScanTask, 321] SingleHostScan caught exception: esxupdate download failed. with code: 1

1. Select an ESX/ESXi host for scanning.
2. Click the Update Manager tab.
3. Click Admin View > Configuration > Network Connectivity.
4. Click IP address or host name for the patch store and enter the appropriate IP address.
5. Rescan the ESX/ESXi host.

• To permanently resolve this issue, ensure the nslookup of the vCenter Update Manager server from the SSH session of ESX/ESXi host can resolve both forward and reverse IP. The DNS entry of the vCenter Update Manager server should be configured properly in the DNS server.
• Ensure that the Update Manager Server can connect to the host on port 902. For information on the port requirements, see VMware Update Manager Network Port Requirement (1004543).

1. Log in to vCenter Server using the vSphere Client.
2. Select the ESX host and click the Configuration tab.
3. Click DNS and Routing.
4. Click Properties.
5. To add a default Gateway, click the Routing tab and enter the appropriate IP address.
6. Click OK.
7. Rescan the ESX/ESXi host.