dns-server in ipv6 dhcp pool

[davega54724]

Hello.  I am trying to configure DHCPv6 on my router for two private development vlans.

My dns servers are offsite and there is no IPv6 other than on my subnets.

How do I configure the dns-server in my IPv6 pool?

For example, my config (IP Addresses changed):

ip dhcp pool vlan3
network 192.168.15.0 255.255.255.0
domain-name mycompany.com
dns-server 192.0.13.50 192.0.28.50
default-router 192.168.15.254
!
ipv6 dhcp pool vlan3
address prefix FDD8:673B:D89B:D15::/64 lifetime 10000 5000
link-address FDD8:673B:D89B:15::/64
domain-name mycompany.com
dns-server ?

How do I add the DNS servers here if they are IPv4 only?

[davega54724]

I just tried setting up a DNS server.

When I try to enter the name in the IPv6 dhcp pool, the router tries to resolve the two addresses.

The router is not connected to my main network at the moment so it is unable to resolve.

Will this work?

Ex:

ip domain-name lab.mycompany.com
ip name-server 192.0.13.50
ip name-server 192.0.28.50
!

ip dhcp pool vlan3
network 192.168.15.0 255.255.255.0
domain-name mycompany.com
dns-server 192.0.13.50 192.0.28.50
default-router 192.168.15.254
!
ipv6 dhcp pool vlan3
address prefix FDD8:673B:D89B:D15::/64 lifetime 10000 5000
link-address FDD8:673B:D89B:15::/64
domain-name mycompany.com
dns-server lab.mycompany.com

[Harold Ritter]

Why not configuring the ipv6 address of the DNS server?

Regards,

[davega54724]

The IPv6 servers are IPv4 only at the moment.
I need IPv6 in our labs. Need to test auto configuration and DHCPv6. Will my example work? I can not use IPv4 addresses in the ipv6 dhcp pool.

[Harold Ritter]

Are the hosts that are getting DHCPv6 configuration also getting DHCPv4 configuration? In other words, are they dualstack? If they are and they are already getting an IPv4 DNS address via DHCPv4, you do not need to configure another DNS in the DHCPv6 configuration. DNS requests will be sent using IPv4 as a transport and will permit both A and AAAA records to be queried.

Regards,

[davega54724]

Ah. That’s good to know. At the moment the sub nets are both IPv4 and IPv6.
How do I make it work if we test with IPv6 only?

[Deepak Kumar]

Hi,

As currently, you are using the dual-stack network (IPv4 and IPv6) in your lab and didn't assign the IPv6 address to the DNS server so it is ok, you will use only IPv4 DNS server. 

But as you mentioned that you want to migrate or use IPv6 network only then we recommend you first migrate your important servers and services in the IPv6 address as DNS server, File server, etc. Now remove or disable the IPv4 DHCP in your network.

Here some points to be noted:

1. IPv4 and IPv6 will not speak each other natively. You will need Dualstack or IPv6 to IPv4 and IPv4 to IPv6 NATing. 

2. If your ISP is providing only IPv4 only then you will be not able to access the internet due to Point 1.

3. DNS server must have AAA records for IPv6 (same as A records in the IPv4) but must be IPv6 forwarded for resolve outside domains for your clients.

[Harold Ritter]

If the host is IPv6 only, you need to provide an IPv6 DNS server in the DHCPv6 configuration.

Regards,

[davega54724]

Thank you for the replies.  Currently the development networks are IPv4 and IPv6.  The DNS servers are offsite and are IPv4 only.  At the moment I can rely on the clients using the IPv4 DNS, but what do I do for a DNS when testing IPv6 only?  If I turn off the IPv4 DHCP, then the clients on the subnets will be IPv6 only and unable to resolve.

How do I use these external IPv4 DNS servers in my IPv6 DHCP pools?

[Harold Ritter]

> How do I use these external IPv4 DNS servers in my IPv6 DHCP pools?

You will not be able to use DNS only reachable via IPv4 in a client that only has IPv6. The options would be to have your own IPv6 enabled DNS servers or to use publicly reachable IPv6 enabled DNS servers like the ones operated by Google or Cloudflare.

https://developers.google.com/speed/public-dns/docs/using

Regards,