IPV6 - SLAAC, DHCPv6 Stateless, DHCPv6 Stateful and M vs O bit

Good day everyone,

I have questions regarding IPv6.

• (1) I implemented Stateful DHCPv6 and the messages went thru (SARR) and clients are getting ip addresses and dhcpv6 options, no problem! Now, I read somewhere that when you are doing this setup, you need to set the M bit flag and this command "ipv6 nd managed-config-flag" should be set in the router so during the RA there will be M bit flag set to 1… But I didn’t enable this on the router and everything looks good… Is it mandatory or is it just a polite way to say to the clients that "ok, I see the M bit set to 1 then I need to use DHCP to make a DHCP request"

I am not really sure if I really need to update the router config with the M bit flag…

• (2) SLAAC – I tested this and I was getting the EUI-64 address no problem, but does SLAAC doesn’t offer DNS just plain ipv6/link-local gateway of the router? For me, it doesn’t makes sense when there is no DNS… I found that I can set the RDNSS from the router and the client was able to get a DNS which I feel happy about it…

• (3) Stateless DHCPv6 – This will still use SLAAC but then it needs additional parameters like DNS… I read somewhere that if you are doing this, you need to set the O bit flag…

So If I enable the O bit flag in the router without configuring the RDNSS and without having a DHCP Pool in the router, How does a client gets the DHCP Option like DNS? Can this be combined with DHCP Relay??

Many Thanks!