NSX-v Host Preparation

The information in this post is based on my NSX Professional experience in the field and from a lecture by Kevin Barrass, a NSX solution architect.

Thanks toTiran Efrat for reviewing this post.

Host preparation overview

Host preparation is the process in which the NSX manager installs the NSX Kernel module inside vSphere cluster and builds the NSX Control plan fabric.

Before the host preparation process we need to complete:

  1. Register the NSX Manager in the vCenter. This process was covered in NSX-V Troubleshooting registration to vCenter.
  2. Deploy the NSX Controllers, covered in deploying-nsx-v-controller-disappear-from-vsphere-client

Three components are involved during the NSX host preparation:
vCenter, NSX Manager, EAM(ESX Agent Manager).

Host Preperation1

vCenter Server:
Management of vSphere compute infrastructure.

NSX Manager:
Provides the single point of configuration and REST API entry-points in a vSphere environment for NSX.

EAM (ESX Agent Management):
The middleware component between the NSX manager and the vCenter. The EAM is part of the vCenter and is responsible to install the VIB (vSphere Installation Bundles), which are software packages prepared to be installed inside a ESXi host.

Host Preparation process

The host preparation begins when we click the “Install” process in vCenter GUI.

host preparation

host preparation

This process is done in the vSphere Cluster level and not per ESXi host. The EAM will create an agent to track the VIB’s installation process for each host. The VIB’s are being copied from the NSX manager and cache in EAM.
If the VIBs are not present in the ESXi host, the EAM will install the VIBs (ESXi host reboot is not needed).
The EAM will remove installed old version VIBs but an ESXi host reboot is needed.

VIBs installed during host preparation:

The ESXi host has a fully working Control Plane after the host preparation was successfully completed

Two control plan channels will be created:

  • RabbitMQMessage bus: provides communication between the vsfwd process on the ESXi hypervisor to NSX Manager over TCP/5671.
  • User World Agent (UWA) process (netcpa on the ESXi hypervisor): establishes TCP/1234 over SSL communication channels to the Controller Cluster nodes.

Host Preperation2

Troubleshooting Host Preparation


EAM fails to deploy VIBs due to misconfigured DNS or no DNS configuration on host.
We may get a status of “Not Ready”:

Not Ready

This indicates “Agent VIB module not installed” on one or more hosts.

We can check the vSphere ESX Agent Manager for errors:

“vCenter home > vCenter Solutions Manager > vSphere ESX Agent Manager”

On “vSphere ESX Agent Manager”, check the status of “Agencies” prefixed with “_VCNS_153” If any of the agencies has a bad status, select the agency and view its issues:


We need to check the associated log  /var/log/esxupdate.log (on the ESXi host) for more details on host preparation issues.
Log into host in which you have the issue, run “tail /var/log/esxupdate.log” to view the log

esxupdate error1

Configure the DNS settings in the ESXi host for the NSX host preparation to success.


TCP/80 from ESXi to vCenter is blocked:

The ESXi host unable to connect to vCenter EAM on TCP/80:

Could be caused by a firewall block on this port. From the ESXi host /var/log/esxupdate.log file:

esxupdate: esxupdate: ERROR: MetadataDownloadError: (‘http://VC_IP_Address:80/eam/vib?id=xxx-xxx-xxx-xxx), None, “( http://VC_IP_Address:80/eam/vib?id=xxx-xxx-xxx-xxx), ‘/tmp/tmp_TKl58’, ‘[Errno 4] IOError: <urlopen error [Errno 111] Connection refused>’)”)

The NSX-v has a list of ports that need to be open in order for the host preparation to succeed.
The complete list can be found in:


Older VIB’s version:

If an old VIBs version exists on the ESXi host, EAM will remove the old VIB’s
But host preparation will not automatically continue.

We will need to reboot the ESXi host to complete the process.


ESXi Bootbank Space issue:

If you try Upgrade ESXi 5.1u1 to ESXi 5.5 and then start NSX host preparation you may face issue and from /var/log/esxupdate log file you will see message like:
“Installationerror: the pending transaction required 240MB free space, however the maximum size is 239 MB”
I faced this issue in customer ISO of IBM blade but may appear in other vendors.

Install fresh ESXi 5.5 Customer ISO. (this is the version i upgrade too)


vCenter on Windows, EAM TCP/80 taken by other application:

If the vCenter runs on a Windows machine, other applications can be installed and use port 80,  causing a conflict with EAM port tcp/80.

For example: By default IIS server use TCP/80

Use a different port for EAM:

Changed the port to 80 in eam.properties in \ProgramFiles\VMware\Infrastructure\tomcat\webapps\eam\WEB-INF\


UWA Agent Issues:

In rare cases the installation of the VIBs succeeded but for some reason one or both of the userworld agents does not functioning correctly. This could manifest itself as:
The firewall showing a bad status OR The control plane between hypervisor(s) and the controllers being down
UWA error

If Message bus service is active on NSX Manager:

Check the messaging bus userworld agent status on hosts by running the command /etc/init.d/vShield-Stateful-Firewall status on the ESXi hosts


Check Message bus userworld logs on hosts at /var/log/vsfwd.log

esxcfg-advcfg -l | grep Rmq

Run this command on the ESXi hosts to show all Rmq variables –there should be 16 variable in total

esxcfg-advcfg -g /UserVars/RmqIpAddress

Run this command on the ESXi hosts, it should display the NSX Manager IP address


Run this command on the ESXi hosts to check for active messaging bus connection

esxcli network ip connection list | grep 5671 (Message bus TCP connection)

network connection



The NSX manager has a direct link to download the VIB’s as zip file:



Reverting a NSX prepared ESXi host:

Remove the host from the vSphere cluster:

Put ESXi host in maintenance mode and remove the ESXi host from the cluster. This will automatically uninstall NSX VIBs.

Note: ESXi host must be rebooted to complete the operation.


Manually Uninstall VIB’s:

esxcli software vib remove -n esx-vxlan

esxcli software vib remove -n esx-vsip

esxcli software vib remove -n dvfilter-switch-security

Note: ESXi host must be rebooted to complete the operation