IPv6 prefix delegation
IPv6 prefix delegation is the mechanism, defined as a DHCPv6 option in RFC 8415, by which an ISP or upstream router hands a shorter IPv6 prefix -- commonly a /56 or /60 -- to a requesting router rather than assigning it a single address. The receiving router, typically a home or office gateway, then subnets that delegated prefix into individual /64 networks for each of its own LAN segments, advertising one to each via router advertisements so devices on that segment can self-assign addresses through SLAAC. This is the step that happens before SLAAC can run at all: a router has nothing to subdivide and advertise until prefix delegation hands it a block in the first place, and a delegation that changes on reconnection -- common with some residential ISPs -- can shift every downstream device's address along with it.
By AdminKit team, Netbase JSC · Updated