Planning with IPv6
Every LAN gets a /64, whatever its size, because address autoconfiguration needs 64 bits for the device part. Providers hand homes a /56 (256 networks) or /48 (65,536 networks).
Plan on nibble boundaries (multiples of 4 bits: /48, /52, /56, /60, /64) so each subnet matches whole hex digits and has its own reverse DNS zone.
Questions
- Why not use smaller subnets than /64?
- SLAAC and privacy addresses stop working, and some devices refuse longer prefixes. Use /127 only for point-to-point router links (RFC 6164).