A Citrix Administrator configured global server load balancing (GSLB) for www.citrix.com, with two ADNS services named Citrix ADC 1 and Citrix ADC 2 in the setup. Which record does the administrator need to add on the parent DNS server to delegate requests from www.citrix.com to Citrix ADC 1 and Citrix ADC 2?

To implement Global Server Load Balancing (GSLB) using the Authoritative DNS (ADNS) method, the Citrix ADCs must become the authoritative name servers for the specific domain being load-balanced (e.g., www.citrix.com). This requires delegating DNS authority from the parent domain's DNS server (e.g., for citrix.com) to the Citrix ADCs. The standard DNS mechanism for this delegation is the Name Server (NS) record. The administrator must create NS records on the parent DNS server that point the subdomain (www) to the ADNS services running on Citrix ADC 1 and Citrix ADC 2.

A. Canonical Name (CNAME): A CNAME record creates an alias for a domain name, it does not delegate DNS authority for a zone to a specific name server.
B. Address (A) record: An A record maps a hostname directly to a static IP address, which would bypass the GSLB intelligence and fail to delegate the query to the ADNS services.
D. Pointer Record (PTR): A PTR record is used for reverse DNS lookups (mapping an IP address to a hostname) and is not relevant for delegating forward DNS resolution.

1. Citrix Product Documentation. (2023). Global server load balancing. Citrix Docs. Retrieved from https://docs.citrix.com/en-us/citrix-adc/current-release/global-server-load-balancing.html.

Reference Section: GSLB deployment types. This section explicitly states: "To use the Citrix ADC appliance as an ADNS server

you must delegate your DNS domain to the GSLB virtual servers... To delegate a DNS domain

create name server (NS) records on your DNS server..."

2. Citrix Product Documentation. (2023). Configuring the Citrix ADC as an ADNS server. Citrix Docs. Retrieved from https://docs.citrix.com/en-us/citrix-adc/current-release/dns/configuring-the-citrix-adc-as-an-adns-server.html.

Reference Section: Introduction. The document states: "To use the Citrix ADC as an ADNS server

you must delegate your DNS domain to the Citrix ADC. To delegate a DNS domain

create name server (NS) records in your existing DNS infrastructure."