SOA Records: These define common parameters for a specific DNS zone.
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- Serial Number: This is used by slave (secondary) servers to check if the zone content is outdated, meaning whether any changes have been made. The serial number must increase by one with each modification. The format is typically the following: the first four digits indicate the year, the next two indicate the month, the following two indicate the day, and the last two indicate the number of changes on a given day.
- Refresh: This interval specifies how often the slave servers should query the primary server to check the current zone serial number.
- Retry: This interval indicates how long the system should wait to retry after a failed refresh attempt.
- Expire: If communication with the primary server fails, this setting determines how long the system will retain the zone information. After this period, the TTL (Time to Live) will apply to the zone records.
NS Records: NS records specify the name servers for a domain. These determine where DNS queries for the domain will be directed. For instructions on how to update NS records for an existing domain, refer to our guide on modifying NS records.
CNAME, A, TXT, CAA Records:
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- A (Address) Record: Primarily used to link a hostname with its corresponding IP address. This assigns an IP address to the domain name.
- CNAME (Canonical Name) Record: Defines an alias for a domain. The DNS query will continue by querying the new name. For example, if a www CNAME example record is in the example.uk zone, www.example.uk is treated as an alias for example.uk. This is helpful if example.uk changes to newexample.uk—you only need to update www CNAME example to www CNAME newexample.
- TXT Record: Contains arbitrary text information enclosed in quotation marks and uses ASCII characters. TXT records are often used for verification purposes, such as email authentication.
MX (Mail Exchanger) Record: Identifies the mail servers responsible for handling email for the domain and specifies priorities for different servers.
SRV Record: The SRV record format is _service._protocol.example.uk
- Service: The symbolic name of the service, always prefixed with an underscore (_).
- Protocol: The IP protocol, typically TCP or UDP, also prefixed with an underscore (_).
CAA Record: This record designates which certificate authorities (CAs) are authorised to issue SSL certificates for the domain, helping control SSL issuance and improve security.