Comment by zrail
4 days ago
(Pedantically) Maximum prefix length of /64 is only required if you want/need SLAAC. If you're assigning static addresses or using DHCPv6 for assignment you can go as small as you want. It's not weird to see /127 for tunnel subnets, for example.
I didn't want to encourage non-standard behavior, but you are correct. Tunnels are a common use the same way /31s can be used in IPv4.
Going smaller than /64 is against best practice and unnecessary. People coming from IPv4 need to understand that trying to be careful with subnet sizing for purposes of preserving space is not a thing in IPv6 below /64. Maybe if a residential user has a /64 from their crappy ISP settings they'd need to do it, but not in a properly configured scenario and certainly not in enterprise.
If you have a network full of static addressed servers, you can go as small as you want. For WiFi networks random devices may connect to, you should just let them pick their own address in a /64 with SLAAC. You may choose to also let servers use SLAAC if you want to, in addition to their static address.