IPv6 is here and confuses me
Your ISP will delegate a prefix for you, probably /48
for your business, unless you have a contract that specifies a different size. For example, 2001:db8:cafe::/48
. You will then break that prefix into separate /64
networks. For a /48
prefix, that means you can have 65,536 different /64
networks: from 2001:db8:cafe::/64
to2001:db8:cafe:ffff::/64
.
It is pretty easy to see which networks belong to you. If any of the first 48 bits delegated to you are different, e.g. 2001:db8:beef::/48
, then you would see that addressing does not belong to you.
With just a couple of exceptions, You will use /64
networks for your IPv6. You could further subnet one or more of your /64
network to /127
for point-to-point links (prevents ping pong attacks) or /128
for things like router loopbacks.