XenDesktop 5 Virtual Machines Do Not Successfully Register with the Desktop Delivery Controller

…. this just says alot about IPv6… i always recommend removing or disabling IPv6 on workstations/servers NIC.’s Well Citrix XenDesktop dosent like it neither… here is why

Symptoms

XenDesktop 5 Virtual Machines do not successfully register with the Desktop Delivery Controller (DDC).

Using Nslookup with the Fully Qualified Domain Name (FQDN) and IP address to the Virtual Desktop Agent and Desktop Delivery Controller returns
correctly.

The firewall or anti-virus software is not causing the issue.

Virtual Desktop Agent is installed with domain administrator account and correct FQDN of Desktop Delivery Controller is entered in Virtual Desktop
Agent configuration.

Desktops do not register.

Pinging the hostname of Desktop Delivery Controller returns an IPv6 address even though IPv6 is disabled on the Network Interface Card (NIC).

Disabling IPv6 on the NIC, and pinging the hostname returns an IPv6 loopback address of : : 1.

Cause

The introduction of XenDesktop 5 supports installations on Microsoft Windows 2008 Server, and the wider implementation of Microsoft Windows 7
desktops. These operating systems have IPv6 enabled in the NIC properties by default.

Resolution

Caution! This fix requires you to edit the registry. Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.

To fully disable IPv6 on the server, desktop, or Virtual Machine, follow the steps below:

Disable IPv6 in the NIC properties by unchecking Internet Protocol Version 6 TCP\IPv6 and click OK.
Click Start, type regedit in the Start Search
box, and then click regedit.exe in the Programs list.
In the User Account Control dialog box, click Continue.
In Registry Editor, locate and then click the following registry subkey:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip6\Parameters\
Double-click DisabledComponents to modify the
DisabledComponents entry.

If the DisabledComponents entry is unavailable, you must create it. To do this, follow these steps:

In the Edit menu, point to New, and then click DWORD (32-bit) Value.
Type DisabledComponents, and then press Enter.
Double-click DisabledComponents.
Type the following value to configure the IPv6 protocol:
Type a hex value of ffffffff to disable all IPv6 components. Then, click OK. The value of 0xffffffff should now be shown (which is correct).
This value also configures Windows 7 to use Internet Protocol version 4 (IPv4) instead of IPv6 in prefix policies.
Reboot to enable your changes.
Once you have rebooted, you can ping the FQDN successfully with it returning the correct IPv4 address and Xen Desktop Virtual Machines should
register successfully with the XenDesktop DDC

Additional information on disabling IPv6 can be found in the following  link from Microsoft: http://support.microsoft.com/kb/929852