How to Monitor DNS Propagation
When you make changes to your DNS records, it can take some time to propagate throughout the internet. This is simply due to the nature of how DNS records are designed to work.
For instance, all DNS records include a TTL value. This value indicates how long the record's data is valid for, before checking for any changes to the data in the record. Once the TTL has expired, if any updates were made to the record (since the last TTL period), then the record will be updated accordingly.
It is important to note that there are many ISPs that store/cache DNS records (for redundancy and efficient processing of DNS requests) within their own name servers/network. They may assign their own TTL, but generally obey the TTL set within the record.
Typically some values (i.e. time since last TTL expired, current TTL value, etc) are unkown and hard to estimate. However, the example scenarios below help to conceptualize the typical behavior and duration of propagation time due to common DNS record changes.
Newly Registered Domain
In the following scenario, you may experience up to 4-24 hours of propagation time. It's also possible that your ISP will update their servers/cache to initialize the domain's records immediately, in which case you would not experience propagation time. However, other users may not be able to immediately access the new domain records, until their ISP's default TTL expires.
- New domain: example.com is registered
- Domain is added to cPanel (DNS records created)
- No DNS records exist in cache/name servers initially
- TTL defaults to the ISP's value, typically between 240-1440 minutes (4 to 24 hours)
A Record Modification
In the following scenario, you may experience up to 20 hours of propagation.
- A Record for example.com points to 188.8.131.52
- A Record for example.com has a TTL of 1440 minutes (24 hours)
- A Record for example.com was cached by the ISP at 12:00 PM EST
- A Record for example.com was changed to point to 184.108.40.206 at 4:00 PM EST (4 hours after TTL 'timer' started)
MX Record Modification
In the following scenario, you may experience up to 13 hours of propagation.
- MX record for example.com points to InMotion Hosting server
- MX record for example.com has a TTL of 1440 minutes (24 hours)
- MX record for example.com was cached by the ISP at 12:00 PM EST
- Changes made to MX record of example.com to point to Google Apps server at 11:00 PM EST (11 hours after TTL 'timer' started)
Monitoring DNS Propagation
An easy way to visualize the propagation of recent changes to DNS records is to perform DNS lookups from various name servers around the world. To do this, you can use a third party tool called the Global DNS Propagation Checker. The instructions below, will guide you through how to use this tool to monitor the progress of propagation of your most recent DNS record changes.
Navigate to https://whatsmydns.net.
Type the DNS record's domain into the search field.
NOTE: The search field will contain www.example.com by default. However, keep in mind that 'www' is considered a sub-domain of example.com in this instance.
Select the type of record you would like to query for, from the drop-down menu. By default, the A record is selected.
Click the Search button.
As the DNS lookup results are returned, the map will begin to generate yellow, green, and red indicators. Yellow indicates 'awaiting results', green indicates 'DNS record propagated', and red indicates 'DNS record not found/propagated'.
The value received for that particular record is displayed next to each geographic location listed on the left. The geographic locations indicate where the name servers queried are located.
Now that you are familiar with using this tool, you can monitor the progress of your DNS record changes through out the internet, globally. This is helpful when troubleshooting why changes to your DNS may be working for you, but not someone else.