Tag: TTL

What is Time To Live (TTL)?

Time To Live TTL

What is TTL?

Time To Live (TTL) sounds like a horror movie, but luckily it is not related to people. It is the value that shows how long the information should be kept in a particular device. There are many pieces of data that have their own TTL value. Here we will see DNS TTL and CDN TTL. 

When we are talking about DNS TTL, it is related to the time that the DNS resolvers must keep the DNS records in their cache. Each of the DNS records will have its TTL value. There are some with longer TTL because there is less chance that the value will change and others with shorter TTL value, where there are often changes. 

You can use these values as an orientation for your DNS records:

  • A and AAAA records – 2 hours (7200 seconds) is ok.
  • CNAME records – up to 12 hours (43200 seconds)
  • MX records – keep it as low. 1 hour (3600 seconds) is ok. 
  • TXT records – up to 12 hours (43200 seconds).

And about the CDN TTL, there we are talking about caching the whole content and how long should the cache servers keep the photos, videos, or whatever needs to be cached. 

When the TTL expires, the servers need to discard the current data that they have and make a new query to get the updated information from the primary servers. 

How does TTL work with DNS queries?

Talking about DNS requests, they are packets of data that also have TTL value. Imagine if they didn’t have such a parameter! The first-ever DNS query could still be around, going from server to server. 

So the TTL value of a DNS request is there to stop the perpetual search or answer and reduce pointless stress on the system. 

The value starts with a bigger number and gets dropped when it comes to zero by the routers. 

How to check the TTL value on Windows?

If you are a Windows user, you can use the Nslookup command and check a particular DNS record like – SOA, A, MX, AAAA, and more. Change the type with the one you want to see.

Start the Command Prompt as an administrator, and use this:

nslookup –types=soa yourdomainhere.com

How to check TTL value on Linux or macOS?

You have more options on Linux and macOS. You can use different commands through the Terminal application. 

The Dig command can show you different DNS records, and you can see their TTL value. This example will be with A DNS record.

dig a yourdomainname.com

You can also use the Host command in a very similar way:

host –a yourdomainname.com

This command will show you all of the visible DNS records with their TTL values.

Conclusion

The TTL value is a necessary part that limits the time a data is valid. It will show if the data is current or if it needs to be updated soon. It makes data updates easier.

 

DNS propagation explained

DNS propagation

Imagine this situation. You have finally decided to truly manage your DNS. You have selected a DNS service provider, you have created master and secondary zones, and you have added all the DNS records that you will need. You spend a lot of time and effort. And after everything is ready, you want to check and… there are no changes! Don’t worry. The DNS propagation takes time.

What is DNS propagation? 

It is a process to update the changes that you make in your DNS. After editing or creating new DNS records, they are saved in the authoritative DNS nameserver. That is ok, but what about all the rest of the DNS name servers? The cache memory of the recursive DNS servers will still keep the older versions of the DNS records based on their TTL value.
The DNS propagation is the time it will take to propagate, to update the changes to all of the recursive name servers.

Frequently asked questions about DNS propagation

Do you have any doubts about the DNS propagation, we hope you can find your answer here:

Could we make the DNS propagation faster?

Of course, we can, but there is a catch. Boosting the speed depends on the TTL value of the DNS records, so lowering the TTL value of each of the DNS records will indeed guarantee faster DNS propagation. The problem is that you might not want to have DNS records with low value. It will stress more your DNS servers, updating them too often.
We don’t need all of our DNS records to update all the time.
It is better to keep the records’ TTL values at their normal level. Plus, editing all of them will take a lot of time.

Can you check if the DNS propagation is ready?

Of course, we can, and this time there is no problem. You need to see if the IP address for a domain name has changed. This will indicate that the A or AAAA records are updated already.
We will show you different ways depending on your OS.

*Change yourdomainname.com with your actual domain name.

Linux or macOS

Open the Terminal, and we will use one of the built-in commands called the Dig command.

dig yourdomainname.com

You can use the host command too, whatever you prefer.

Windows OS
The Terminal alternative in Windows is the Command Prompt. Inside it, we will use the NSlookup command.

nslookup yourdomainname.com

How long can the DNS propagation take?

It can take a long time. Depending on when the recursive DNS servers updated themselves and the TTL values of the DNS records, it can take as much as 72 hours.

Conclusion

Waiting for the DNS propagation to occur is a time-consuming process that we could not fully predict. This is the situation, and there is little we can do, so just be patient, and in less than 72 hours, the update will happen.
Patience is the key here!

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