On 30/07/2020 12:13, Remco Rijnders wrote:
An IPv6 address is 128 bits in length. Usually an ISP allocates 64
bits to a single customer, allowing the systems on/behind that
connection to automatically assign themselves an address based on
their MAC address for example. Note that also allocations bigger than
64 bits are common so customers get 70 or 76 bits to use and can use
multiple subnets on their home/business networks.
I don't think an ISP is supposed to allocate less ...
As I understood it, the first 64 bits are the "network address", ie
sort-of assigned to the edge router, and the remaining 64 bits are
assigned by the network operator.
So in your scenario of customers getting more bits, they are effectively
being assigned 2^6 or 2^12 network addresses. Exactly the scenario
planned for high-level ISPs parcelling out address space to low-level ISPs.
And looking at the wikipedia page, it looks like the ISP *must* allocate
at least a /64, because the spec says each device allocates itself a
least-significant-64 address at random using a collision-detect
protocol. Which is why many simplistic algorithms include the MAC
address to (try to) guarantee a unique address on the first attempt.
Cheers,
Wol
