DNS (Domain Name System)

DNS operates at the Application Layer, i.e., Layer 7 of the ISO OSI model. DNS traffic uses UDP port 53 by default and TCP port 53 as a default fallback

• A record: The A (Address) record maps a hostname to one or more IPv4 addresses. For example, you can set example.com to resolve to 172.17.2.172.

• AAAA Record: The AAAA record is similar to the A Record, but it is for IPv6. Remember that it is AAAA (quad-A)

• CNAME Record: The CNAME (Canonical Name) record maps a domain name to another domain name. For example, www.example.com can be mapped to example.com or even to example.org.

• MX Record: The MX (Mail Exchange) record specifies the mail server responsible for handling emails for a domain.

When you type an address.com your browser will query the DNS server for the A record.

When you try to send an email to [e-mail] the mail server will query DNS server for MX record