What are CNAME (Canonical Name) Records?
CNAME records, also known as Alias records, point a hostname to another hostname or FQDN. They are called Alias records because they point to other records that have the mapping for that domain. When a name server looks up a domain and finds it is a CNAME record, it replaces the name with the canonical name (the target of the CNAME) and looks up the new name. In a sense, a CNAME lookup performs two queries to reach the final resolution.
CNAME records are commonly used to point multiple hostnames to a single location. This is useful when you have multiple records pointing to the same location (usually a web server at the root of a domain). If that location changes, all you have to do is change the endpoint in the record you’re pointing all those CNAME’s to. CNAME records can also be used to point a host name to a location that is external to the domain.
Please note, the value field must end in a dot (.) in order to keep the root domain from being appended to the end of the value.
As per RFC 1035, CNAME records must be unique and cannot share the same FQDN with any other record.
How to Configure a CNAME Record
1.Select Managed DNS and click on Domains
2. Select the Domain Name you want to add a CNAME record too.
3. Under the CNAME Records section, click the to add a record.
4. In this screen, you will add the record information. Follow the steps below:
A) Name: This will be the hostname for your record. It is important to note, the domain name is automatically appended to the “Name” field of the record. Note the name field is required, because a CNAME record can not be defined for the root record of the domain.
B) TTL: Edit the TTL. Time to Live is measured in seconds and is the amount of time the record will cache in resolving name servers and web browsers.
C) Record Mode: The Record Mode will be left at Standard for this tutorial. Please note, the other Record Mode options are covered in different tutorials.
D) Host: Enter the destination host you would like this CNAME record to resolve too.
E) Note: Add a helpful note with keywords so you can search for your records later.
F) Save and Close: Save your changes. Don’t forget to commit your changes.
Records that are static and don’t change often should have TTL’s set between 1800 (being on the low end) to 86400 seconds (30 minutes to 1 day cache).
Records configured with Failover or that change often should have TTL’s set anywhere from 180 to 600 (3 to 10 minutes cache).
If a change is needed for a record with a high TTL, then the TTL can be lowered prior to making the change and then raised back up again after the changes were made.