Well, up to this point I'm a bit confused of how to do IPv6 Subnetting outside nibble boundaries with specific hosts numbers.

Lets say that i have a /64, and that i want to divide it in 3 subnets, 2 WAN and 1 LAN, the LAN needs to be able to handle 2000 hosts, and well, the WANS are 3 hosts wide.

The first thing that i do is to determine how many bits i require,so, for the Wans is 2 bits, and for the lan is 11 bits.

Soo, i will start from the LAN /64+11=/75 :XXXX XXXX XXX0 0000:: So first address will be= 1000:: and last address will be= FFE0:: (from left to right) So, between First and last address there are enough hosts for my LAN

then.. WAN1

first: FFF0::

last: FFF8::


first: FFFC::

last: FFFE::

in both WAN cases, i left reserved bits at the right... so for the first i do like this :1111 1111 111X X000:: second: :1111 1111 1111 1XX0::

What i don't really get is then, i have a /75 for LAN1.. /77 for Wan1... /79 for WAN2, which makes no sense at all, as in both cases, that masks can handle LOTS of IP... Then.. based on what i have seen online, is that the mask goes in the opposite way (which makes sense), so instead of a /64 + how many bits, is 128-how many bits... In which case the bits match how many host i want to fit... but all those examples do the "subneting" from right to left.... so its possible to do as i want?

  • In most cases, IPv6 networks will be /64, else you break some IPv6 features. The exceptions are /127 for point-to-point links, and /128 for loopbacks.
    – Ron Maupin
    Commented Jan 13 at 20:04
  • See this answer, this answer, etc. Please search the site.
    – Ron Maupin
    Commented Jan 13 at 20:16
  • Mathematically, bits are bits, so subnetting is the same in v6 as v4. There are just more of them, and v6 introduces some special cases. (SLAAC requires a /64, but you can ignore that.) Nibble boundary subnets are a convenience for your sanity. (the global pool 2000::/3 is an obvious exception)
    – Ricky
    Commented Jan 14 at 6:59


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