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ALIAS (often referred to as ANAME) and CNAME are DNS record types used to point a domain name (or subdomain name) to another name.
Similarities of CNAME and ALIAS records
- Referring function: both CNAME and ALIAS are used to refer requests from one domain name to another. Instead of pointing directly to an IP address, they redirect to another hostname.
- Useful for load balancers and content delivery networks (CDNs): Both record types are commonly used to redirect traffic to infrastructure such as load balancers or CDNs without changing the actual domain.
- Transparency for end users: it is usually transparent to end users whether a CNAME or an ALIAS is used. They simply enter the desired domain name and are redirected to the appropriate resource.
- Dynamic IP addresses: Both CNAME and ALIAS are useful when the underlying IP address of the destination is dynamic and subject to change. Instead of referencing the IP address directly, they reference a hostname, which then resolves to the current IP.
Differences between CNAME and ALIAS records
CNAME record (Canonical Name)
The CNAME record is commonly used to point subdomains or hostnames to another hostname. For example:
In this example, `server123.hostingcompany.com` refers to `www.example.com`.
Limitations of the CNAME record
- CNAME records cannot be used for the domain (root element) itself, but only for subdomains.
- In CNAME record can refer only to a host name (FQDN - Fully Qualified Domain Name), not to an IP address.
- A domain name can have only one CNAME record.
- A CNAME cannot exist together with other records with the same name. This means that if www.beispiel.de has a CNAME, it cannot have other records (such as MX for e-mail) under the same name.
The ALIAS record, is a special DNS record type often used to solve the problem that a CNAME record cannot point to the root (apex/main) element of a domain.
Advantages of the ALIAS record
An ALIAS can co-exist with other DNS records. This means you can have www.example.com as ALIAS for server123.hostingfirma.com and at the same time set other DNS records for www.beispiel.de.
The ALIAS record allows one domain to point to another domain or IP address. Thus, both indirectly have the same IP settings (A and AAAA record).
In this example, example.com points to target.example.net