The Domain Name System (DNS) is one of the most confusing parts of running an online business but also one of the most critical parts.
At its core, DNS is like a telephone directory - it resolves a name that a human can understand (e.g. www.marketplacer.com) into an address that a computer can understand (e.g. 104.198.108.154).
Domains and DNS
When you buy a domain, the registrar will often also bundle DNS services as part of your purchase or they may charge extra for it. A domain can have many multiple sub-domains these are parts at the start of a web address - e.g. www, webmail or shop. Each subdomain can point to a different physical server - that way your webmail and your website can happily coexist without knowing anything about each other.
DNS records
A DNS 'record' is one entry in our big internet phonebook - it maps a single subdomain to a single address. For example, the 'www' subdomain of 'marketplacer.com' points to 104.198.108.154 while the 'support' subdomain of 'marketplacer.com' points to marketplacer.zendesk.com which, in turn, points to 34.216.174.56.
In this case, www is called an A record (the A stands for "Address"). What that means is that the 'www' record points directly to an address that the computer understands (104.198.108.154).
By contrast, support is called a CNAME record (this is short for Canonical Name). That means that the 'support' record points to another record (the 'marketplacer' subdomain of the 'zendesk.com' domain).
You notice that each of these records has a subdomain – what if we want people to access our domain without a subdomain (e.g. 'https://marketplacer.com/')? That's a special subdomain called the "apex" of the domain. Some providers will use the special @ symbol to represent the apex, while others will just leave it blank.
One final type of record you might encounter is a wildcard record - this is represented by using a * as the subdomain. This will match ANY subdomain - so you can have bob.marketplacer.com, frank.marketplacer.com, jane.marketplacer.com, jodie.marketplacer.com and alice.marketplacer.com all pointing to the same address with a single record.
Editing DNS Records
The process for editing DNS records varies by each provider so it's impossible to list ever instruction here. Each provider's own help center should give you instructions on how they edit DNS records. However, there are some core concepts that apply to most providers:
You can add/delete or edit records. You cannot (in most cases) have two records for the same subdomain (e.g. you cannot have both an A and a CNAME record for the 'www' subdomain).
You will need to enter three pieces of information:
- The subdomain you want to add/edit (e.g. 'www')
- The type of record to add/edit (e.g. 'CNAME', 'A')
- The address/destination for the record (e.g. '104.198.108.154' or 'marketplacer.zendesk.com')
DNS Propagation
Unfortunately, it's not as simple as just editing your DNS records. Because there are DNS servers all over the world, it takes time for changes to propagate across the internet. How long it takes is controlled by a special field in a DNS record called a TTL (time-to-live) which is recorded in seconds. This tells every DNS server around the world how long to hang onto the records they have for your domain. Sometimes this can be as long as 24 hours.
With a bit of planning, you can arrange to reduce the TTL to a low number before you make a change and then increase it again later. But in the worst case, it can just be a waiting game. You can check on the progress of DNS propagation across the world using a tool like www.whatsmydns.net.