IPv6 subnet calculator

IPv6 CIDR range for 2001:b000::/21

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 2001:b000::/21

The prefix identifies a network with 107 host bits. Every address from the first address through the last address belongs to this range.

CIDR prefix

2001:b000::/21

Network mask

ffff:f800::

Prefix length

/21

Host bits

107

First address

2001:b000::

Last address

2001:b7ff:ffff:ffff:ffff:ffff:ffff:ffff

Total addresses

162259276829213363391578010288128

Total addresses (human readable)

2^107 addresses (162,259,276,829,213,363,391,578,010,288,128; about 162.25 nonillion)

How this range is calculated

  1. 1The /21 prefix keeps the first 21 network bits fixed.
  2. 2Setting all 107 host bits to zero produces 2001:b000::.
  3. 3Setting those host bits to one produces 2001:b7ff:ffff:ffff:ffff: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

2001:b000:0000:0000:0000:0000:0000:0000

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