External users attempting to connect to their virtual desktops through Citrix Gateway are met with the error:

"Unable to start your desktop. Gateway authentication failed because the gateway for this <desktop FQDN> can't be located. Contact your help desk with error code 2091-2523."

This error indicates that the Citrix Gateway is unable to resolve the Fully Qualified Domain Name (FQDN) of the virtual desktop they are trying to access. Consequently, the authentication process fails, and the desktop launch is prevented. This issue specifically impacts remote users accessing their desktops via the Gateway.

• Access the NetScaler Administration Console: Log in to the administrative interface of your Citrix NetScaler appliance.

• Navigate to DNS Settings - Nameserver: Locate the DNS configuration section within the NetScaler console. This is typically found under the "System" or "Network" settings, often within a subsection labeled "DNS" or "Name Servers."

• Add the Necessary DNS Name Servers: Identify the DNS servers within your internal network that are authoritative for resolving the FQDNs of your virtual desktops. Add the IP addresses of these DNS servers to the NetScaler's list of configured name servers. Ensure you add all necessary DNS servers for redundancy and reliable resolution.

• Save the NetScaler Configuration: After adding the DNS name servers, save the changes to the NetScaler configuration. This ensures the new DNS settings are applied.

• Test VDI Launch: Instruct the users who were experiencing the error to attempt launching their virtual desktops through the Citrix Gateway again. Verify that they can now successfully connect to their desktops without encountering the "Unable to start your desktop" error.

Problem Cause

The root cause of this error is often related to the NetScaler appliance's inability to resolve the internal FQDNs of the virtual desktops. To rectify this, you need to ensure the NetScaler is configured with the appropriate DNS name servers that can successfully look up these internal addresses.