I read a bit about IPv6 and found that usually you get assigned a /48 prefix address. Which gives you 16 bit for subnetting.

Reading further assuming that you use /64 subnets you would end up with 65535 possible subnets with a lot of IP-Addresses in each of these.

My question is, how you deal with scenarios where 65535 Subnets are not sufficient. I mean you have to consider, that even small subnets need to have a /64 mask in order to not break the automatic IPv6 mechanisms.

For example: In IPv4 we could use a subnet mask of /25 and end up with 131072 individual subnets with each having 126 host inside. Each separated via Layer 3. With IPv6 it seems there are less possibilities to separate hosts at layer 3.

I know that IPv6 offers way more hosts in each subnet but how do you separate or restrict those hosts on the same network from talking to each other?

Are there additional features to do this? Would be great if somebody could point me in the right direction.

Thank you.

  • If you don't need Internet routability, each IPv6 Unique local address prefix allows 65536 subnets, and you can have basically as many prefixes as you want. Dec 1, 2021 at 18:46

1 Answer 1


If your address plan could use more, ask your LIR or ISP, they can accommodate you. Possibly reach 64 thousand /64s is an indication you could more comfortably use a larger prefix. Plan for the future.

One subnet is one size fits all, a /64. Not reserving 64 bits for the host part will break things, and is not necessary.

End users need multiple /64s. Everyone does, a corporate campus plus regional offices, small business, or home user. RIRs will recommend to keep it simple, with a /48 per site or customer. ARIN bumps your assignment up to the next hex digit (/44, /40) well in advance by it being strictly necessary based on numbers of /48s.

Site is not well defined, but could be any organizational unit that could use 4 hex digits of address space to play in.

Consider that Hurricane Electric's 6in4 tunnel service assigns a /48 for free. IANA has only started on a fraction of the available address space, and there already is enough for every person on the planet to have thousands of /48s.

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