Subnets·IPv6 /97
IPv6
/97
2,147,483,648

IPv6 /97 prefix

/97 means the first 97 bits are the network and 31 are left for hosts. That is 2,147,483,648 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
/97
Host bits
31
Addresses
2,147,483,648
Usable hosts
2,147,483,648
/64 networks inside
None
Nibble boundary
No

Prefixes either side

/942^342^34/952^332^33/964,294,967,2964,294,967,296/981,073,741,8241,073,741,824/99536,870,912536,870,912/100268,435,456268,435,456

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 /97?

2,147,483,648, of which 2,147,483,648 can actually be handed out.

Q. How is a /97 written?

IPv6 uses no mask — you simply write /97.

Q. How many /64 networks fit in a /97?

None — it is narrower than a /64.

Q. How many host bits are there?

31. Each extra network bit halves the addresses.