On Oct 22, 2010, at 12:55 AM, Mark Smith wrote: > On Fri, 22 Oct 2010 15:52:08 +1100 > Karl Auer <ka...@biplane.com.au> wrote: > >> On Thu, 2010-10-21 at 21:05 -0500, Jack Bates wrote: >>> On 10/21/2010 8:39 PM, Ray Soucy wrote: >>>> >>>> How so? We still have RA (with a high priority) that's the only way >>>> DHCPv6 works. I guess there is a lot of misunderstanding about how >>>> DHCPv6 works, even among the experts... >>> >>> Actually, the last I checked, there are implementation of DHCPv6 without RA. >> >> I'll go out on a limb here and say that RA is not needed for DHCPv6. >> > > RAs are still needed to convey the M/O bit values, so that end-nodes > know they need to use DHCPv6 if necessary. As there are two address > configuration methods, there is always going to be a need to express a > policy to end-nodes as to which one they need to use. > You can actually force a client to assume the M bit if you cause it to launch a DHCPv6 client through other means. You don't have to have RA for that. Policy can be expressed by RA, or, it can be expressed by other means.
>> A DHCPv6 client multicasts all its messages to the well-known >> all-relays-and-servers address. A client needs only its link-local >> address to do this. The relay (or server if it happens to be on the same >> link) can thus talk to the client in the complete absence of RA. >> > > There isn't a method to specify a default gateway in DHCPv6. Some > people want it, however it seems a bit pointless to me if you're going > to have RAs announcing M/O bits anyway - you may as well use those RAs > to announce a default router too. > Actually, it's not pointless at all. The RA system assumes that all routers capable of announcing RAs are default routers and that virtually all routers are created equal (yes, you have high/medium/low, but, really, since you have to use high for everything in any reasonable deployment...) There are real environments where it's desirable to have a way to tell different clients on a network to use different default gateways or default gateway sets. Owen