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Re: IPv6 RA vs DHCPv6 - The chosen one?
From: Glen Kent <glen.kent () gmail com>
Date: Tue, 20 Dec 2011 15:28:24 +0530

When a router needs to learn information from another router it will
*usually* use the RA messages and not DHCPv6, as the latter is
*usually* meant for Router - Host communication. However, it is NOT
uncommon to see hosts also learning the information using RA messages.
Router's afaik dont usually act as DHCP clients and thus information
that can only be passed in DHCPv6 may not be available to the routers,
and you may need an alternate mechanism.

Glen

On Tue, Dec 20, 2011 at 11:57 AM, Ravi Duggal <raviduggal2906 () gmail com> wrote:
Hi,

IPv6 devices (routers and hosts) can obtain configuration information
about default routers, on-link prefixes and addresses from Router
Advertisements as defined in   Neighbor Discovery.  I have been told
that in some deployments, there is a strong desire not to use Router
Advertisements at all and to perform all configuration via DHCPv6.
There are thus similar IETF standards to get everything that you can
get from RAs, by using DHCPv6 instead.

As a result of this we see new proposals in IETF that try to do
similar things by either extending RA mechanisms or by introducing new
options in DHCPv6.

We thus have draft-droms-dhc-dhcpv6-default-router-00 that extends
DHCPv6 to do what RA does. And now, we have
draft-bcd-6man-ntp-server-ra-opt-00.txt that extends RA to advertise
the NTP information that is currently done via DHCPv6.

My question is, that which then is the more preferred option for the
operators? Do they prefer extending RA so that the new information
loaded on top of the RA messages gets known in the single shot when
routers do neighbor discovery. Or do they prefer all the extra
information to be learnt via DHCPv6? What are the pros and cons in
each approach and when would people favor one over the other?

I can see some advantages with the loading information to RA since
then one is not dependent on the DHCPv6 server. However, the latter
provides its own benefits.

Regards,
Ravi D.



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