Mysterious missing DHCPv6 feature, was Re: How does one obtain an IPv6 DNS server when VPNing to an ASA?

[Gert Doering]

Hi,

On Tue, May 18, 2010 at 04:35:44AM -0700, David Barak wrote:
> Here we disagree.  In IPv4-land, a whole bunch of functions are
> handled via DHCP, and modifications in a simgle place (the DHCP
> server) can affect a whole bunch of remote clients without any other
> necessary changes.  RA+DHCPv6 requires congruent configurations in
> N places, where N >= 2 always, and for large scale enterprises N
> is much greater than 2.  

This claim is surely nice, but just plain wrong.

At initial configuration time:

 - with RA+DHCP: you touch every router (to enter the prefix configured on
   the interface, set the "other-config bit", turn on DHCP relay), and the 
   DHCP server

 - with DHCP: you touch every router (to enter the prefix configured on
   the interface, turn off RA, turn on DHCP relay), and the DHCP server

If you change DHCP options, like "who is the NTP server":

 - with RA+DHCP: you touch the DHCP server

 - with DHCP: you touch the DHCP server

If you change network options, like "what is the prefix used in a given
facility":

 - with RA+DHCP: you touch every router to configure the new prefix

 - with DHCP: you touch every router to configure the new prefix

Maybe my creativity is a bit limited, but please tell me what sort of
configuration change you have in mind that would affect a different
number of devices for "RA+DHCP" vs. "DHCP-only".


(DHCP Prefix Delegation could indeed make setup in a large network a lot
more automatic, but that is a somewhat independent discussion on the 
method used to configure hosts on the LAN)

Gert Doering
        -- NetMaster
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