Wildcard '*' versus Exact Match '@' DNS records

Ever wondered what the difference was between the ‘@’ symbol and the ‘*’ symbol when setting up a DNS Zone file for a domain name.  In the past I have seen them used interchangeably with sometimes unexpected results.

The difference is that one (@) is for exact match search where there is no subdomain and the other (*) is a Wild Card – they are not interchangeable in all circumstances.

 Consider the following Zone File for domain name xyz.com,  

•  Any DNS request for an MX (mail) record for xyz.com (with no prefix) will return the two MX records mx1.mailserver.com and mx2.mailserver.com
  
  
•  Any DNS request for an MX (mail) record for the subdomain branch.xyz.com will return the two MX records mx3.mailserver.com and mx4.mailserver.com
  
  
•  If an A record request for the hostname ‘xyz.com’ is made, an exact match for this record with no subdomain is used (@) and it will return the IP address 103.6.216.204.
  
  
•  If an A record request for the hostname ‘www.xyz.com’ is made, an exact match for this subdomain is used and it will return the IP address 103.6.216.205
  
  
• If an A record request for any other hostname  e.g.  ‘branch.xyz.com’ is made, the wildcard record (*) is used it will return the IP address 103.6.216.203.

 In summary then;

 The prefix ‘@’ refers to the domain name itself -- it essentially means no prefix.

  The prefix * is a wildcard -- if a DNS request is made for an address that does not have a specific A record setup, then the wildcard IP address will be returned.