On the Networking & Security > Installation > Host Preparation tab or Service Deployment tab, the installation status appears as Not Ready on the clusters and hosts. Clicking the Resolve option does not fix the problem.


  • Clicking the Not Ready link shows error as VIB module for agent is not installed on the host.

  • ESXi host fails to access VIBs from the vCenter Server.

  • While changing from vShield Endpoint to NSX Manager, you may see  status as Failed.


  1. Verify that the DNS is configured correctly on the vCenter Server, ESXi hosts and the NSX Manager. Ensure that the forward and reverse DNS resolution from the vCenter Server, ESXi hosts, NSX Manager and the vSphere Update Manager are working.
  2. To determine if the problem is related to DNS, review the esxupdate logs and look for the message “esxupdate: ERROR: MetadataDownloadError:IOError: <urlopen error [Errno -2] Name= or service not known in the esxupdate.log file.

    This message indicates that the ESXi host is unable to access the vCenter Server's Fully Qualified Domain Name (FQDN). For more information, see Verifying the VMware vCenter Server Managed IP Address (1008030).

  3. Verify that Network Time Protocol (NTP) is configured correctly.  VMware recommends configuring NTP. To determine whether NTP out of sync issues are impacting your environment, check the /etc/ntp.drift file in the NSX Manager support bundles with version 6.2.4 and later.
  4. Verify that all ports required for NSX for vSphere 6.x are not blocked by a firewall.  For related information, refer to:  

    VMware vSphere 6.x supports VIB downloads over port 443 (instead of port 80). This port is opened and closed dynamically. The intermediate devices between the ESXi hosts and vCenter Server must allow traffic using this port.

  5. Verify that the vCenter Server Managed IP Address is configured correctly.  For more information, see Verifying the VMware vCenter Server Managed IP Address (1008030).
  6. Verify that the vSphere Update Manager is working correctly. Beginning with vCenter Server 6.0U3, NSX installation and upgrade procedures no longer leverage vSphere Update Manager with ESX Agent Manager. VMware strongly recommends running at least vCenter Server 6.0U3 or later. If you cannot upgrade, ensure that the vSphere Update Manager service is running. You can configure the vSphere Update Manager bypass option, as per KB 2053782.
  7. If you specify non-default ports while deploying vCenter Server, ensure that these ports are not blocked by the ESXi host firewall. 
  8. Verify that vCenter Server vpxd process is listening on TCP port 8089. NSX Manager supports only the default port 8089.