Subnets·IPv6 /101
IPv6
/101
134,217,728

IPv6 /101 prefix

/101 means the first 101 bits are the network and 27 are left for hosts. That is 134,217,728 addresses.

Addresses are 128 bits, so nobody writes a mask — only the prefix length. A home gets a /56, a single network a /64.

Prefix
/101
Host bits
27
Addresses
134,217,728
Usable hosts
134,217,728
/64 networks inside
None
Nibble boundary
No

Prefixes either side

/981,073,741,8241,073,741,824/99536,870,912536,870,912/100268,435,456268,435,456/10267,108,86467,108,864/10333,554,43233,554,432/10416,777,21616,777,216

How to read this

  • /24 means the first 24 bits are the network; the remaining 8 hold the addresses inside it.
  • Each extra bit splits the network in two and halves the addresses.
  • Usable addresses are normally the total minus two — the network and broadcast addresses.
  • IPv6 has no broadcast, so nothing is subtracted. One network is conventionally a /64.

Frequently asked questions

Q. How many addresses are in a /101?

134,217,728, of which 134,217,728 can actually be handed out.

Q. How is a /101 written?

IPv6 uses no mask — you simply write /101.

Q. How many /64 networks fit in a /101?

None — it is narrower than a /64.

Q. How many host bits are there?

27. Each extra network bit halves the addresses.