IPv6 Glossary

IP addresses let machines communicate across a network. DigitalOcean Droplets are assigned IPv4 addresses by default. Enabling IPv6 on a Droplet gives you access to its 16 additional IPv6 addresses.


This glossary defines the core concepts behind IPv6 to help build your mental model of how IPv6 work and understand what the documentation is referring to when it uses certain terminology.

A Fully Qualified Domain Name (FQDN), or Absolute Domain Name, is a complete domain name that identifies a host or server.
IPv4, or Internet Protocol version 4, is a networking protocol that maps 32-bit IP addresses to devices on a network. IPv4 routes most of the network traffic on the internet.
IPv6, or Internet Protocol version 6, is a networking protocol that maps IP addresses to devices on a network. IPv6 is the most recent version of the IP protocol and greatly expands the available address space compared to IPv4.
PTR records, or pointer records (also known as reverse DNS or rDNS records), map an IP address to a domain name. PTR records are used for reverse DNS lookups.
Simple Mail Transfer Protocol (SMTP) is a messaging protocol which controls how email transmissions are performed between computers in Transmission Control Protocol/Internet Protocol (TCP/IP) networks.
A subnet, or subnetwork, is a network within another network meant to simplify routes between devices on a network.
A subnet mask splits an IP address, such as 255.255.255.0, into host and network addresses. The bits (digits) in a subnet mask indicates the number of bits that have been alloted to the network’s address and the number of bits available for host addresses in the network.