dnscontrol/documentation/alias.md

ALIAS Records

ALIAS records are not widely standardized across DNS providers. Some (Route 53, DNSimple) have a native ALIAS record type. Others (Cloudflare) implement transparent CNAME flattening.

DNSControl adds an ALIAS record type, and leaves it up to the provider implementation to handle it.

A few notes:

1. A provider must "opt-in" to supporting ALIAS records. When registering a provider, you specify which capabilities you support. Here is an example of how the cloudflare provider declares its support for aliases:

func init() {
    providers.RegisterDomainServiceProviderType("CLOUDFLAREAPI", newCloudflare, providers.CanUseAlias)
}

2. If you try to use ALIAS records, all dns providers for the domain must support ALIAS records. We do not want to serve inconsistent records across providers.
3. CNAMEs at @ are disallowed, but ALIAS is allowed.
4. Cloudflare does not have a native ALIAS type, but CNAMEs behave similarly. The Cloudflare provider "rewrites" ALIAS records to CNAME as it sees them. Other providers may not need this step.
5. Route 53 requires the use of R53_ALIAS instead of ALIAS.
6. Azure DNS requires the use of AZURE_ALIAS instead of ALIAS.