R1配置：
ipv6
interface GigabitEthernet0/0/0
ipv6 enable
ipv6 address auto global
ipv6 route-static 2001:21:: 64 2001:12::1
R2配置：
ipv6
dhcp enable
dhcpv6 pool test
address prefix 2001:21::/64
excluded-address 2001:21::1
interface GigabitEthernet0/0/0
ipv6 enable
ipv6 address 2001:12::1/64
undo ipv6 nd ra halt
interface GigabitEthernet0/0/1
ipv6 enable
ipv6 address 2001:21::1/64
dhcpv6 server test
