IPv6 Address Range Calculator

About this interactive

An IPv6 address announces its type in its first hextet. Global unicast, 2000::/3: the first three bits are 001, so the first hextet runs from 2000 to 3fff. That leaves 125 bits, 2^125 addresses. These are public and unique in the world. A company usually gets a /48 from its ISP, numbers its subnets in the next 16 bits (the fourth hextet, 65,536 of them, counted in hex: 9 is followed by a, and f by 10) and keeps the last 64 bits for interfaces. Unique local, fc00::/7: the first seven bits fixed, so the address starts fc or fd (fd in practice), 2^121 addresses, routed inside an organization only. Link-local: fe80 with zeros to the 64th bit, then 64 interface bits, from fe80:: to fe80::ffff:ffff:ffff:ffff. Good on its own link only. Multicast, ff00::/8: every address starting ff, 2^120 of them. Three special addresses: ::1 is loopback (one address, where IPv4 sets aside 127.0.0.0/8), :: is unspecified (all zeros, used before a host has an address), and ::/0 is the default route, matching everything. The video writes the global unicast range as 200::/3 with the bits 0001; it is 2000::/3, and the fixed bits are 001. Type address types exactly as each question names them, hex in either case, and exponents and counts as numbers. Anything you miss shows the answer and how to work it out. Seven of the twenty-four questions are drawn each run.

What you'll learn

Name an IPv6 address's type from its first hextet: global unicast (2000::/3), unique local (fc00::/7), link-local (fe80) or multicast (ff00::/8)
Work out the bounds and sizes of the IPv6 ranges, the /48 and /64 split, hex subnet numbering, and the loopback, unspecified and default route addresses

Aligned to

Cisco CCNA

1.9 Describe IPv6 address types

1.8 Configure and verify IPv6 addressing and prefix

Cisco CCST Networking

2.3 Identify IPv6 addresses and prefix formats

CompTIA Network+

3.4 Given a scenario, implement IPv4 and IPv6 network services

Key terms

Global Unicast Address: A publicly routable IPv6 unicast address beginning with the prefix 2000::/3, equivalent in role to a public IPv4 address, used to identify a device uniquely across the internet. GUAs are assigned by ISPs and regional internet registries and are the addresses used for internet-facing communication in IPv6.
Unique Local Address: An IPv6 address in the FC00::/7 range (most commonly FD00::/8) used for private internal network communication, analogous to IPv4 private address ranges like 192.168.0.0/16. Unique local addresses are not routable on the public internet but can be routed within an organization's own network.
Link-Local Address: An IPv6 address in the FE80::/10 range that is automatically assigned to every IPv6-enabled interface and used only for communication within a single network link. It cannot be routed beyond the local Layer 2 segment and is required for Neighbor Discovery and router communication.
IPv6 Multicast Address: An IPv6 address in the FF00::/8 range used to deliver packets to multiple subscribed interfaces simultaneously.
IPv6 Loopback Address: The reserved IPv6 address ::1/128 that a device uses to send traffic to itself, allowing the local network stack to be tested without sending packets onto a physical network. It is the IPv6 counterpart of IPv4's 127.0.0.1, but reserves a single address rather than the whole 127.0.0.0/8 range, and a packet addressed to ::1 never leaves the device.
Unspecified Address: The IPv6 address ::/128 (all zeros), used to indicate the absence of an address, typically before a device has been assigned one.
Default Route: A catch-all routing entry represented as 0.0.0.0/0 (IPv4) or ::/0 (IPv6) that a router uses to forward packets when no more specific matching route exists in the routing table. It is typically configured to point toward the next-hop router or ISP connection.
IPv6 /48 Prefix: An IPv6 address block assigned by an ISP that reserves 48 bits for the network portion, leaving 16 bits for subnet IDs and 64 bits for host addresses.
IPv6 Prefix Length: A value expressed in slash notation that identifies how many leading bits of an IPv6 address represent the network portion, functioning similarly to CIDR notation in IPv4.

Topics

Ipv6 Global Unicast Address Unique Local Address Link Local Address Multicast Ipv6 Prefix Length Interactive Calculation

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