calculating autoconf ipv6 address with ipv6calc

Here’s how ipv6calc did the job.

$ ipv6calc --in prefix+mac --action prefixmac2ipv6 2001:470:19:13c::/64 AB:CD:EF:12:34:56 --out ipv6addr
2001:470:19:13c:a9cd:efff:fe12:3456/64