CIDR mapping

Classless Inter-Domain Routing (CIDR) mapping uses the IP addresses of the requesting nameserver to provide IP-specific CNAME entries, allowing you to direct internal users to a specific environment or direct to the origin. Providing different responses to an internal corporate DNS infrastructure, such as internal test environments and another answer for all other name servers, is a common use for CIDR mapping.

CIDR maps split the Internet into multiple CIDR-block zones. Properties that use a map can specify a handout CNAME for each zone on the property's editing page.

Note: To configure a property for CIDR mapping, your domain must have at least one CIDR map defined. Because GTM nameservers accept connections over both IPv4 and IPv6, you may need to add both IPv4 and IPv6 CIDRs to your map to achieve desired functionality.