What is DNS Propagation?

Whether it’s for a new DNS configuration, you’re switching service providers, or you need to change an IP address or hostname, there are times DNS records require updates. When record changes occur, they need to propagate in order for new information to be visible to users. This resource will cover the ins and outs of DNS propagation so you can plan your record changes accordingly.

DNS Propagation Meaning

DNS propagation is the time period in which it takes updates to DNS records to be in full effect across all servers on the web. The reason changes aren’t instantaneous is because nameservers store domain record information in their cache for a certain amount of time before they refresh. While your domain won’t experience any downtime from properly planned record changes, some users will still be served a cached version of your site until all servers have propagated.

DNS Propagation Time

So, how long does the propagation process take? There’s no concrete answer for this, but typically DNS propagates within a few hours, though it can take as long as 72. The timeframe for propagation depends on several factors, including your internet service provider (ISP), your domain’s registry, and the TTL values of your DNS records.

How Internet Service Providers (ISPs) Affect DNS Propagation Times

When a request is sent for a domain, it is first passed to a local resolver, typically that of an ISP, and then on to several different servers before reaching an authoritative server that holds the final answer for the original request. The problem is that some ISPs ignore Time to Live (TTL) values and keep records in cache past the designated TTL expiration in a record. This can slow propagation down significantly.

How Domain Name Registry Affects the Speed of DNS Propagation

Anytime you make changes to the authoritative nameserver for your domain, the changes also have to climb the proverbial DNS ladder. Even after your update is propagated on your provider’s network, the new information needs to be picked up by the Top Level Domain (TLD) and the root servers.

Tip: To avoid unnecessary downtime when switching providers, we recommend waiting 72 hours before deleting records from your previous provider or discontinuing your old service.

How TTL Affects Global DNS Propagation

As mentioned above, some ISPs ignore TTL in DNS records, but even if they didn’t, propagation is still affected by TTL values. The higher your TTL is set, the longer propagation will take. For instance, if your DNS record has a TTL of 86,400 seconds (24 hours) and you make a change to the record, all servers will continue to serve end users the old information until the 24 hours is up. Once the TTL has expired, servers will make a new DNS request to retrieve any new information.

If your domain makes regular updates to your DNS records, having a high TTL would be a disadvantage—especially if an ISP ignores the TTL values. In this case, a lower TTL is advisable. Recommended TTL for domains that make frequent record changes would be 30 to 300 seconds. The lower the better for mission-critical services. It is possible to set TTL below 30 seconds, but many resolvers will not recognize values less than that, so you’d want to make a test record first.

Global DNS Propagation Checker

To make sure your DNS record changes have propagated globally, you can use an online DNS Propagation checker. There are several to choose from and it’s a good idea to check more than one. Here are a few propagation checkers:

DNS Tool Box by Constellix

DNS Checker

whatsmydns.net

MX Toolbox

DNS Propagation Check

Global DNS Checker

nslookup.io

How DNS Propagates on the Constellix Network

At Constellix, any changes made to your DNS records are propagated instantly across all of our authoritative nameservers in our global network. This allows you to configure lower TTL values, which in turn, helps speed up propagation time. However, recursive resolvers will still be operating with the information they have in cache until TTL expires on the updated DNS record.

Propagation Wrap Up

By now, your mind should be fully “propagated” with the necessary information about how DNS propagation works. Keep in mind how TTL values and nameservers affect the process, and you’ll be able to plan seamless DNS record changes for your domain.