IPv6 subnet calculator

IPv6 CIDR range for 1900::1640/123

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 1900::1640/123

The prefix identifies a network with 5 host bits. Every address from the first address through the last address belongs to this range.

CIDR prefix

1900::1640/123

Network mask

ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffe0

Prefix length

/123

Host bits

5

First address

1900::1640

Last address

1900::165f

Total addresses

32

Total addresses (human readable)

2^5 addresses (32)

How this range is calculated

  1. 1The /123 prefix keeps the first 123 network bits fixed.
  2. 2Setting all 5 host bits to zero produces 1900::1640.
  3. 3Setting those host bits to one produces 1900::165f.

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

1900:0000:0000:0000:0000:0000:0000:1640

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