IPv6 Address

An IPv6 address is the sixth version of the Internet Protocol and the successor to IPv4. It is a 128-bit number, which yields a pool on the order of 340 undecillion addresses — practically inexhaustible. It is written in hexadecimal as eight groups of four characters separated by colons, for example 2001:0db8:85a3:0000:0000:8a2e:0370:7334.

The advantages of IPv6

The main reason IPv6 was created was the exhaustion of the public IP address pool in version four. The vast address space removes the need for widespread NAT — every device can receive its own public address. IPv6 also simplifies packet headers, supports automatic address configuration (SLAAC), and natively organizes security and multicast mechanisms. To keep the notation shorter, leading zeros in a block can be omitted, and one run of all-zero blocks can be replaced by a double colon (::).

In practice, most infrastructure runs in dual-stack mode, handling IPv4 and IPv6 in parallel, because the two protocols are not directly compatible with each other.

IPv6 addresses in practice

In domain configuration, an IPv6 address is stored in an AAAA record, the counterpart of the A record for IPv4. Serving a site over IPv6 improves availability for users on networks that support only that protocol and is increasingly a standard in modern hosting. Modern VPS servers usually receive a pool of IPv6 addresses that you configure in DNS alongside IPv4. Remember that firewall rules and rate limits must be defined separately for IPv6, since addresses from that pool are not covered by rules written for IPv4, and more mobile and ISP networks now offer IPv6-only connectivity.