I know an IPv6 host will send Router Solicitation (RS) messages, and a router on the link will reply Router Advertisement (RA) messages.
In the RA message, there is the Source Link-Layer Address and Prefix Information in options. So a host can know the router's MAC address, and it can generate it's IPv6 address.
How can a host know the router's IPv6 address (router's link-local or global address)?
The RA IPv6 packet will have the router address as the source IPv6 address.
A host doesn't really need to know the router's IP address to send packets to other hosts. On a LAN, frames are sent to a layer-2 (MAC) address. The layer-3 IPv6 packet will have the destination host IPv6 address, not the router address. If a host is on a different LAN, the packet will still have the destination host IPv6 address, but the frame will have the destination MAC address of the router.
