Understanding DNS Propagation

It can take time before changes to DNS records will take effect. DNS propagation is complex, but there are a few tips that can help.

The term "propagation" is a misnomer in the sense that DNS does not actively push new records around the internet when you change them. Services that deal with DNS records ask for and forward information upon request. They then use something called a TTL (Time to Live) to determine how long to wait before asking again.

Tip 1: If you expect that you will be changing an existing record, you will want to reduce the TTL settings for that record ahead of time. You will want a small value such as 5 minutes (300 seconds). Smaller values might be ignored. You will still have to wait until the old TTL expires however before the new TTL takes effect.

Tip 2: If you are about to change DNS information, resist the temptation to query the information ahead of time. DNS servers will keep track of the query and the fact that a record was not found. You will then have to wait the full TTL before any servers involved in the query will look again to see if the record now exists. This could been the difference between seeing your new record immediately or having to wait a day or two before the changes are visible.