Networks and addresses
IPv6 prefix sizes (/64, /48, /32)
What the number after the slash means in IPv6, and why /64 is a single network, /48 a site, /32 an ISP.
An IPv6 prefix is written as the address followed by the number of fixed bits: 2a0e:1234::/48. The smaller the number, the bigger the block.
A /64 is one network segment. It is the unit that stateless autoconfiguration (SLAAC) needs, so every LAN, VLAN or VM bridge gets its own /64; splitting it further breaks address autoconfiguration. A /56 or /48 is what a site gets: 256 or 65,536 of those /64s, enough for every network a company will ever have. A /32 is the typical allocation to an ISP or hosting company, which hands /48s to its customers.
The RIPE NCC assigns PI space from /48 and allocates PA space to members from /32. There is no reason to be stingy: a /48 per customer site is the design intent, and address space is not what runs out in IPv6.