No additional OSPFv3 command is needed to include a second IPv6 prefix that has been configured on an interface in the OSPFv3 process. If OSPFv3 is configured on an interface, and a second IPv6 address is added to the interface, the second address is automatically included in the OSPFv3 process.
2
Yes, two routers can become adjacent if they are configured with different prefixes. No prefix information is included in Hellos, the source address of the Hello packet is the Link-local address. Other IPv6 addresses configured on the interfaces have no bearing on whether two routers become adjacent or not.
3
The basic router configurations are
RtrA:
ipv6 unicast-routingint e 0/0ipv6 address 2001:db8:0:4::3/64ipv6 ospf 1 area 1int e 0/1ipv6 address 2001:db8:0:5::1/64ipv6 ospf 1 area 1
RtrB:
ipv6 unicast-routingint e 0/0ipv6 address 2001:db8:0:4::2/64ipv6 ospf 1 area 1int e 0/1ipv6 address 2001:db8:0:6::1/64ipv6 ospf 1 area 1
RtrC:
ipv6 unicast-routingint e 0/0ipv6 address 2001:db8:0:4::1/64ipv6 ospf 1 area 1int serial 0/0ipv6 address 2001:db8:0:8::1/64ipv6 ospf 1 area 0
RtrD:
ipv6 unicast-routingint s 0/0ipv6 address 2001:db8:0:8::2/64ipv6 ospf 1 area 0
4
To change area 1 to a totally stubby area and summarize into area 0, new router configurations are
RtrA:
ipv6 unicast-routingint e 0/0ipv6 address 2001:db8:0:5::3/64ipv6 ospf 1 area 1ipv6 router ospf 1area 1 stub
RtrB:
ipv6 unicast-routingint e 0/0ipv6 address 2001:db8:0:4::2/64ipv6 ospf 1 area 1ipv6 router ospf 1area 1 stub
RtrC:
ipv6 unicast-routingint e 0/0ipv6 address 2001:db8:0:4::1/64ipv6 ospf 1 area 1int serial 0/0ipv6 address 2001:db8:0:8::1/64ipv6 ospf 1 area 0ipv6 router ospf 1area 1 stub no-summaryarea 1 range 2001:db8:0:10::/61