How to add static IPv6 in Oracle cloud

Question

I am running OS Ubuntu 18.4. I will add static ipv6 address with netplan in Oracle cloud my netplan yaml file looks like this:

network:
  version: 2
  renderer: networkd
  ethernets:
    enp0s3:
      accept-ra: no
      addresses:
        - 10.0.0.XX/24
        - 2603:c020:8003:XXX:e9af:d0dc:XXXX:eac6/128
      gateway4: 10.0.0.1
      gateway6: 2603:c020:8003:XXX::1
      nameservers:
        addresses: [8.8.8.8,8.8.4.4]

I can ping the ipv6 address but can not connect to the Internet, I can add IPv6 address over the Oracle cloud GUI, but these addresses have a valid and expiration time, I want to add addresses with a forever lifetime.