I will explain it. As an example I have two devices whose ip are 192.168.100.10 ( Ipv6 - 2001:xxxx:xxxxx:xxxx:7654) and another is 192.168.100. ( Ipv6 - 2001:xxxx:xxxxx:xxxx:9990). and I made two host names tv.freeddns.org and pc.freeddns.org and I assigned two separate ipv6 with my two hosts. like tv.freeddns.org with Ipv6 - 2001:xxxx:xxxxx:xxxx:7654 and for pc.freeddns.org with Ipv6 - 2001:xxxx:xxxxx:xxxx:9990 and it run perfectly. But if I restart my router then both ipv6 ip are the same. I cannot use ipv4 because my ISP does not give me a public ipv4 ip address.

I have attached a screenshot also. Please help me. how to solve this issue.