IPv6
/7
2^121
IPv6 /7 prefix
/7 means the first 7 bits are the network and 121 are left for hosts. That is 2^121 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
- /7
- Host bits
- 121
- Addresses
- 2^121
- Usable hosts
- 2^121
- /64 networks inside
- 2^121
- Nibble boundary
- No
Blocks reserved at this length
Blocks the standards set aside. The addresses themselves are the same everywhere, so they are left as they are.
fc00::/7
Prefixes either side
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 /7?
2^121, of which 2^121 can actually be handed out.
Q. How is a /7 written?
IPv6 uses no mask — you simply write /7.
Q. How many /64 networks fit in a /7?
2^121.
Q. How many host bits are there?
121. Each extra network bit halves the addresses.