IPv6 is adding lots of complexity IPv4 never have to deal with.
SLACC, interface-specific link-local address both look good in paper but cause lots real life headache.
When it works, it works; when it don't, you have to unlearn and relearn everything network before you could possibly understand the problem, let alone fixing them.
You can use DHCPv6 instead of SLAAC. Plenty of people seem to find SLAAC preferable... and interface-specific link-local addresses are key to making it work so...
SLACC, interface-specific link-local address both look good in paper but cause lots real life headache.
When it works, it works; when it don't, you have to unlearn and relearn everything network before you could possibly understand the problem, let alone fixing them.