IPv6
/48
2^80
IPv6 /48 prefix
/48 means the first 48 bits are the network and 80 are left for hosts. That is 2^80 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
- /48
- Host bits
- 80
- Addresses
- 2^80
- Usable hosts
- 2^80
- /64 networks inside
- 2^80
- Nibble boundary
- Yes
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 /48?
2^80, of which 2^80 can actually be handed out.
Q. How is a /48 written?
IPv6 uses no mask — you simply write /48.
Q. How many /64 networks fit in a /48?
2^80.
Q. How many host bits are there?
80. Each extra network bit halves the addresses.