1Y0-201 · Question #91
Scenario: A Citrix Administrator discovers that NO Desktop OS machines can register against a specific Delivery Controller, Controller4, after maintenance over the weekend. The administrator logs…
The correct answer is B. Windows Firewall is improperly configured. When a single Delivery Controller rejects VDA registrations while all its services are running and other controllers work normally, the most likely cause is a host-based firewall blocking the required registration ports on that controller.
Question
Scenario: A Citrix Administrator discovers that NO Desktop OS machines can register against a specific Delivery Controller, Controller4, after maintenance over the weekend. The administrator logs into Controller4 and finds all services are running. Pooled Desktop OS machines are registering with other Delivery Controllers in the environment and users are able to connect successfully. What is preventing the Desktop OS machines from registering with Controller4?
Options
- ASQL Server is offline.
- BWindows Firewall is improperly configured.
- CController4 was removed from NetScaler load balancing configuration.
- DThe Active Directory machine account for Controller4 was deleted from Active Directory.
How the community answered
(46 responses)- A15% (7)
- B72% (33)
- C4% (2)
- D9% (4)
Why each option
When a single Delivery Controller rejects VDA registrations while all its services are running and other controllers work normally, the most likely cause is a host-based firewall blocking the required registration ports on that controller.
If SQL Server were offline, the entire site would be impacted and VDAs would fail to register with all Delivery Controllers, not just Controller4.
VDA registration requires TCP communication (typically port 80 for older versions or port 443 with SSL) between the VDA and the Delivery Controller. If Windows Firewall on Controller4 was misconfigured during weekend maintenance - for example, a rule was removed or a profile was changed - inbound registration traffic would be silently dropped, causing all VDAs targeting that controller to remain unregistered while other controllers remain unaffected.
Removing Controller4 from the NetScaler load balancing configuration would prevent clients from being directed to it, but VDAs use direct FQDN-based registration and would still be able to reach Controller4 directly.
If the Active Directory machine account were deleted, Kerberos authentication for that controller would fail, but the administrator's successful login to Controller4 and running services indicate the machine account is intact.
Concept tested: Delivery Controller firewall configuration for VDA registration
Source: https://docs.citrix.com/en-us/citrix-virtual-apps-desktops/technical-overview/communication-ports.html
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