IPv6 subnet calculator

IPv6 CIDR range for fc00::/66

Calculate the network address, final address, mask, and exact address capacity of any IPv6 CIDR prefix.

Example: 2606:4700::/32

Host bits are normalized to the network address before the range is calculated.

CIDR calculation

Network details for fc00::/66

The prefix identifies a network with 62 host bits. Every address from the first address through the last address belongs to this range.

CIDR prefix

fc00::/66

Network mask

ffff:ffff:ffff:ffff:c000::

Prefix length

/66

Host bits

62

First address

fc00::

Last address

fc00::3fff:ffff:ffff:ffff

Total addresses

4611686018427387904

Total addresses (human readable)

2^62 addresses (4,611,686,018,427,387,904; about 4.61 quintillion)

How this range is calculated

  1. 1The /66 prefix keeps the first 66 network bits fixed.
  2. 2Setting all 62 host bits to zero produces fc00::.
  3. 3Setting those host bits to one produces fc00::3fff:ffff:ffff:ffff.

Network address

The normalized prefix base

CIDR notation describes a network, not a single host. If an address with host bits set is entered, this calculator normalizes it to the network base before calculating the range.

Expanded network address

fc00:0000:0000:0000:0000:0000:0000:0000

Recent network calculations

Recent IPv6 CIDR Ranges

Open recent IPv6 prefixes to inspect their normalized range, mask, and address capacity.

Learn how IPv6 CIDR notation and subnet ranges work