A TTL, or Time to Live, is a setting in every DNS record that dictates how long the record will be cached by resolving nameservers, browsers, etc.
Resolving name servers are the middlemen of the DNS exchange. When you enter a domain into your browser, you are actually asking your local resolving name server for the IP address of that domain.
If someone has recently made the same request, the information will likely be stored in the resolving name server’s cache. If it isn’t, then the resolving name server will ask the name server authoritative for that domain –usually the DNS provider.
Once the record pointing the domain to the corresponding IP address has been found, that information is stored on the resolving name server. This speeds up the resolution time for the next time the domain is queried at that resolver.
The TTL is set in seconds, so 60 is one minute, 1800 is 30 minutes, etc..
Here are some general guidelines for setting your TTL’s:
- Static IP’s/hostnames should have a TTL of 1800 or higher.
- Dynamic IP’s/hostnames should have a TTL of 1800
The lower the TTL the more often a client will need to query the name servers for your host’s (record’s) IP address this will result in higher query traffic for your domain name. Whereas a very high TTL can cause downtime when you need to switch your IP’s quickly.
Tip: If you plan on changing your IP you should set your TTL to a low value a few hours before you make the change. This way you won’t have any downtime during the change. Once your IP is changed you can always raise your TTL to a higher value again.
Read Best Practices for TTL’s on our blog.