Hub:

interface Tunnel123
 ip address 172.16.123.1 255.255.255.0
 no ip redirects
 ip nhrp map multicast dynamic
 ip nhrp network-id 1
 ipv6 address FE80::123:1 link-local
 ipv6 address 1230::1/16
 ipv6 nhrp map multicast dynamic
 ipv6 nhrp network-id 1
 tunnel source Ethernet0/2
 tunnel mode gre multipoint
 tunnel key 1


Spoke 1:
interface Tunnel123
 ip address 172.16.123.2 255.255.255.0
 no ip redirects
 ip nhrp map 172.16.123.1 11.1.1.1
 ip nhrp map multicast 11.1.1.1
 ip nhrp network-id 1
 ip nhrp nhs 172.16.123.1
 ipv6 address FE80::123:2 link-local
 ipv6 address 1230::2/16
 ipv6 nhrp map 1230::1/16 11.1.1.1
 ipv6 nhrp map multicast 11.1.1.1
 ipv6 nhrp network-id 1
 ipv6 nhrp nhs 1230::1
 tunnel source Ethernet0/2
 tunnel mode gre multipoint
 tunnel key 1
!

Spoke 2:
interface Tunnel123
 ip address 172.16.123.3 255.255.255.0
 no ip redirects
 ip nhrp map 172.16.123.1 11.1.1.1
 ip nhrp map multicast 11.1.1.1
 ip nhrp network-id 1
 ip nhrp nhs 172.16.123.1
 ipv6 address FE80::123:3 link-local
 ipv6 address 1230::3/16
 ipv6 nhrp map 1230::1/16 11.1.1.1
 ipv6 nhrp map multicast 11.1.1.1
 ipv6 nhrp network-id 1
 ipv6 nhrp nhs 1230::1
 tunnel source Ethernet0/2
 tunnel mode gre multipoint
 tunnel key 1