Hello may (legally) occur situation when router is not sending router advertisements but is providing configuration via DHCPv6?
According to RFC4862, Sec 5.5.2 this can happen. However:
- DHCPv6 does not have an option to provide address of default gateway (explained at the same reference), so in this case default gateway must be configured manually.
- if the router want to disable SLAAC and use DHCPv6 instead, the proper way would be to use a special bit in router advertisement, that disables SLAAC. To do this you set M flag (AdvManagedFlag) on the router advertisement and disable all A flags (AdvAutonomousFlag) on each prefix. See RFC4861 for the description of flags. More info here
- you might want to consider this link as well.