What is DNS propagation?
When you update the nameservers for a domain, it may take up to 24-48 hours for the change to take effect. This period is called DNS propagation. In other words, it is a period of time ISP (Internet service provider) nodes across the world take to update their caches with the new DNS information of your domain. Due to DNS caches of different levels, after the nameservers change, some of your visitors might still be directed to your old server for some time, whereas others can see the website from the new server shortly after the change.
Why does it take up to 72 hours?
Let’s imagine you live in Bari, Italy, and you just have changed the nameservers for your domain that is hosted in Phoenix, USA. When you open your domain in a web browser, your request is not going to the hosting server directly, it has to pass through several ISP nodes first. So your computer starts by checking local DNS cache, then the request is sent to your local Bari ISP. From there, the request goes to the upstream provider in Rome, Italy, then connects to the ISP in Hamburg, Germany. After that, the request is sent to the first receiving point in the USA – New York, NY and ultimately, to the ISP in Phoenix, AZ.
What are the ways to pass DNS propagation?
There are three basic methods that will allow you to pass the DNS propagation.
If you HAVE NOT changed the nameservers and do not wish them to propagate for so long, there is a way to reduce the propagation time. You need to do two simple things:
- Point your domain to the destination IP address by means of A record on the side of the current DNS provider, setting the minimal TTL ('Time to live' – propagation time) for this record, for instance, to 300 seconds (5 minutes).
- Once A record has been updated, wait up to 30 minutes and change the nameservers for your domain.
As a result, your domain will be resolved to your previous host from the places where the propagation has not been completed yet and to a new one – from the places where it has already passed. In such a way, you may avoid a downtime as both hosts will show you the same result – your new website.
How do I know when propagation is complete?
Unfortunately, there are no tools available to track name server propagation. Even a Whois check, ping, and traceroute test cannot indicate whether the propagation is complete. Certain tools similar to WhatsMyDNS give you some information regarding name server propagation. However, it may not show you accurate and complete information.
Factors that affect DNS propagation time include:
- Your TTL (Time to Live) settings — You can set the TTL for each DNS record in your domain name's zone file. TTL is the time period for which servers cache the information for your DNS records. For example, if you set the TTL for a particular record to one hour, servers store the information for that record locally for an hour before retrieving updated information from your authoritative nameserver. Shorter TTL settings make can increase propagation speed. However, shorter settings also increase the number of queries to your authoritative nameserver, and that increased load slows your server's processing time.
- Your ISP (Internet Service Provider) — Your ISP caches DNS records (stores the data locally rather than retrieving fresh data from your DNS server) to speed up Web browsing and reduce traffic, which slows your propagation time. Some ISPs ignore TTL settings and only update their cached records every two to three days.
- Your domain name's registry — If you change your domain name's nameservers, we relay your change request to the registry within minutes, and they publish your authoritative NS (nameserver) records to their root zone. Most registries update their zones promptly. For example, VeriSign refreshes zones for .com domain names every three minutes. However, not all registries make updates that quickly. Registries often protect their root nameservers from overuse by setting a high TTL of up to 48 hours or more for those NS records. In addition, even though recursive nameservers should not cache the root NS records, some ISPs cache the information anyway, which can result in a longer nameserver propagation time.
There is another way to check if the DNS propagation is completed for you. You need to run one of the following commands from your PC, laptop or other devices: