Impact on removing IPV6 DNS Server from client terminals when Dual-stack is enabled

[Duleep Thilakarathne]

Hi,

This is not an issue but just to get ideas from experienced bind resources.
Please ignore this question, if it is out of the scope of this
mailing thread.

Significant number of DNS requests can be observed when dual-stack enabled
and send both IPV4 and IPV6 DNS server addresses to clients through DHCP or
similar.


According to RCF 4472,

"Note that even though IPv6 DNS resolver discovery is a recommended

   procedure, it is not required for dual-stack nodes in dual-stack
   networks as IPv6 DNS records can be queried over IPv4 as well as
   IPv6.  Obviously, nodes that are meant to function without manual
   configuration in IPv6-only networks must implement the DNS resolver

   discovery function."

client DNS request possibilities  as follows per domain. (client
browser/Application may send all or selected queries in parallel with short
time difference)

1. A record requests to primary ipv4 dns server

2. A record request to secondary ipv4 dns

3. AAAA record requests to primary ipv4 dns server

4. AAAA record request to secondary ipv4 dns

5. A record requests to primary ipv6 dns server

6. A record request to secondary ipv6 dns

7. AAAA to primary ipv6 dns server

8. AAAA to secondary ipv6 dns server


What will happen,  if IPV6 DNS server addresses  are removed from DHCP or
similar assignment in dual-stack scenario and only keep IPV4 DNS servers. I
guess this will reduce load to DNS servers as well as SP networks. Are
there any practical limitations ?. Is it mandatory to send both IPV4 and
IPV6 DNS server addresses in a dual-stack scenario.


Regards

DT
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