Hello Ray,
In the RS, the source MAC address is the host’s MAC address, the destination is the “all routers multicast” destination FF02::2.
About the “shutdown procedure”, I just labbed this up to see how it works. Take a look at this wireshark capture:
https://www.cloudshark.org/captures/69fd7a31fe57
The first packet (length 118) is a regular router advertisement. The second packet (length 102) is sent when the interface is shut but also when you reload the router.
The difference between the two is that in the “goodbye” router advertisement, all ICMPv6 options are removed except for the prefix information. Also, the router lifetime is set to 0.
This seems to be specified in the RFC:
A Lifetime of 0 indicates that the router is not a default router and SHOULD NOT appear on the default router list.
I couldn’t find anything in the RFC about withdrawing options as a requirement so that might be specific to Cisco.
Hope this helps!
Rene