The default-link-metric for IPv6 depends upon the multi-topology configuration.
No multi-topology: The IPv6 default-link-metric is the same as that configured for IPv4 address-family.
Multi-topology: The IPv6 default-link-metric is equal to the value configured for IPv6 address-family.
Multi-topology transition: The IPv6 default-link-metric will be equal to the value configured for IPv6 address-family.