[CentOS] IPv6 updating DNS

Fri Oct 3 03:45:35 UTC 2014
David G. Miller <dave at davenjudy.org>

Bill Gee <bgee at ...> writes:

> 
> On Wednesday, October 01, 2014 15:23:52 Mark Tinberg wrote:
> > > All of my servers and
> > > workstations are able to ping6 to outside targets, and anything with a
> > > browser installed can open ipv6.google.com.
> > > 
> > > So far I have figured out that you have to run TWO instances of DHCP.  
One
> > > instance issues IPv4 and the other issues IPv6.    I have not gone so 
far
> > > as to actually set up a second instance of DHCP.
> > 
> > As long as you run a router advertisement daemon clients will self-
assign
> > routable addresses, you don't really need DHCPv6 if you are also running
> > DHCPv4, you can set DNS (even an IPv6 DNS server) or any other
> > configuration using the DHCPv4 daemon.
> > 
> > —
> > Mark Tinberg
> > mark.tinberg <at> wisc.edu
> 
> That is true - radvd does cause all my systems to self-assign a public 
IPv6 
> address.  The problem is that radvd does NOT cause my DNS to get those 
> addresses.  The result is I can use IPv6 internally only by giving the 
> address.  I cannot use it by hostname.  
> 
> The only exception is the server hosting DNS.  DNS somehow knows the IPv6 
> address of its host and will deliver it on demand.  I can ssh to that 
server 
> by name and get an IPv6 connection.
<SNIP>
Ran into this a couple of years ago when I was playing with IPv6.  I guess 
it hasn't changed since then.  

The problem is that dhcpd and dhcpd6 are two separate services and dhclient 
only talks to one of them.  So, you can get your client IPv4 addresses into 
DNS or you can get your IPv6 addresses in but not both through DHCP and 
dynamic DNS updates.  There is probably a way to get both addresses in using 
a shell script that runs on each client but I didn't see a way to do it 
securely.

Cheers,
Dave