Domain Name System

Learn what DNS is, and how to utilize it to configure your domain name to Pantheon's servers.

Contributors: Alex Fornuto.

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Pantheon does not offer DNS management services. However, we can help you to understand how DNS works, and configure your domain to point to your Pantheon site.

DNS Provider Instructions

DNS Terminology

TLD

Stands for Top Level Domain. This is the last piece of your website URL (.com, .net, .org, etc)

Registrar

The service through which you purchase a domain name. Most registrars also offer DNS management services.

Domain

The last section of your website name before the TLD, the domain is what you purchase from the Registrar.

Subdomain

Separate by periods (.), subdomains precede the domain name. www is the most commonly seen subdomain. Subdomains can also stack (example: www.something.example.com).

Authoritative Name Server

The service that publishes your domain's DNS records

DNS Record Types

NameDescription
APoints a domain or subdomain to an IPv4 address.
AAAAPoints a domain or subdomain to an IPv6 address.
CNAMEPoints a domain or subdomain
MXUsed to specify email servers. Note that Pantheon does not offer email services, so your MX records shouldn't be pointed at Pantheon.
TXTThese are generic records, used by many services for different things.
NSSpecifies where the authoritative name servers for this domain are.

DNS Propagation

Every DNS record has a Time To Live (TTL) value, which specifies how long any DNS server should hold that record, before dropping it and asking for a new version from its upstream DNS provider. TTLs are usually set in seconds with a few common ones being 86400 (24 hours), 43200 (12 hours), 3600 (1 hour), and 500 (5 minutes).

DNS Propagation is the time it takes for changes made to DNS records to be reflected across DNS servers globally. A lower TTL value means faster propagation, but it's important to note that it is not a 1:1 ratio. Between your authoritative name server and the DNS servers of any particular ISP could be any number of intermediate DNS servers. Each server in that chain will wait for the records it holds to expire before requesting new ones. Because of this, it can take several times longer than your record's TTL value to see changes reflected for everyone.

DNS Migration Preparation

Follow these simple steps to help minimize DNS-related downtime when you're planning a site migration:

  1. Lower the TTL values as low as allowed (usually 500) several days in advance at your DNS service manager. That way when the values are changed, new records are propagated faster.

  2. Use dig to confirm the new TTL values have propagated to your ISP's DNS servers:

    dig +nocmd +noall +answer pantheon.io
    pantheon.io.            60      IN      A       23.185.0.2

    In the example above, the TTL of the A record forpantheon.io is 60 seconds.

  3. Raise the TTL values back to 3600 (24 hours) after the migration is complete to improve stability in case of a DNS service outage.

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