3.1.b (v) Global Prefix Configuration Feature
The goal of this function is to simplify network renumbering and lets you automatically configure prefixes on interfaces.
EN conf t ipv6 general-prefix myglobalprefix 2000:1:1::/48 int lo1 ipv6 address myglobalprefix 0:0:0:1::1/64 int lo2 ipv6 address myglobalprefix 0:0:0:2::1/64
Now you can change the global prefix for both via 1 command:
no ipv6 general-prefix myglobalprefix 2000:1:1::/48 ipv6 general-prefix myglobalprefix 2000:2:2::/48
The above command automatically fills in the first 48 bits of the address, then adds all 0s until it is /64. Finally We use EUI-64 to complete the whole IPv6 address.