I have ros7. What should I put in the ND DNS server. I thought I would put whatever DNS IP I want to advertise. But it never work. Some suggested put a ipv6 address of the router. Please clarify. Thank you
Your understanding is correct, see RFC 8106 for details.
Note, that not all hosts can extract DNS information from Router Advertisement messages. You likely want both DHCPv6 server options and ND option.
Thank you. I configured the DNS servers with the local ipv6 address. Do I need to enabled advertise DNS option in ND? I also added the options code 23 and value with the local ipv6 as the value. Do I need to do anything at the IP/DNS settings?
You do not have to, as RDNS servers can be set up on hosts administratively. Having them advertised via DHCPv6 and/or Neighbor Discovery is solely at your discretion based on your situation.
The DNS parameter in Neighbor Discovery is, in general, useful in simple setups where there is no DHCPv6 at all and hosts configure IPv6 via SLAAC.
I would have set both for better compatibility though.
If I don’t include DNS server in the ND or DHCPv6 option 23, host don’t show the IPv6 DNS server. They will not able to resolve any URL. Host will have to set the DNS server manually. Most people don’t know the IPv6 DNS server address, therefore, It was good idea for me to include as part of the DHCP setting. I just don’t understand why I should include a local ipv6 address instead of an actual IPv6 DNS server address in order for it to work. Thoughts? Thank you
IIRC as long as it’s a valid IPv6 address of an actual RDNS server then it should work.