There are six “SuperPoP” core routers; these are used when giving out /48 prefixes to customers, e.g.:

2001:708:0KLM::/48

“K” here is the number of the regional SuperPoP. This is not meant to be used for aggregation purposes, rather than to just create some mild hierarchy for the addresses, rather than allocate them in a sequential fashion.

“L” is the sequential number of customers within the SuperPoP. “0” is reserved.

“M” is reserved for expanding the number of customers in the SuperPoP and/or increasing the size of the assignment to the customers. To maintain future flexibility, this is still zero.

When assigning the prefix to the customers, Funet recommends they keep the first four bits (the first nibble) zero for now.

An example of a customer assignment is 2001:708:510::/48.