Re: Results: Straw poll: autoconf vs manual conf

On 1-okt-2007, at 19:35, Brian Dickson wrote:

> I'm a bit confused by the above. It might be terminology, or your  
> use of it, but either way, it would be helpful to give some  
> examples of IOS server(s) and IOS client(s), doing DHCPv6 vanilla,  
> and DHCPv6 with PD.

You mean something like this?

!
interface Ethernet1
  ipv6 address autoconfig
  ipv6 dhcp client pd dhcpv6prefix
!
interface Ethernet2
  ipv6 address dhcpv6prefix 0:0:0:A0::/64 eui-64
!

See my message earlier today for the URL for my book that I took this  
from.  :-)

This bit of config tells the router to be a stateless autoconfig  
client on ethernet1 and to ask a DHCPv6 server for a prefix. Note  
that prefix delegation and address assignment are two completely  
different features, it's not just a case of setting the prefix length  
to 128.

The resulting prefix is stored in the variable dhcpv6prefix and  
subsequently used to number interface ethernet2, which will then  
automatically send out router advertisements using the /64 in  
question. Note that bits 56 - 63 are set to A0 here which means the  
prefix that is received must be at least a /56.

IIRC, the RAs reuse the DHCP timers so renumbering becomes very easy.

> Will assignments only occur if the prefix is /64?
> What happens if the PD is something other than /64? E.g. a /80, or  
> a /120, for examples.

In the example above you need a /56. I haven't tested it, but I  
assume a longer prefix will work if you set the ethernet2 prefix  
length to something small enough except that if you send out RAs with  
a prefix other than /64 the hosts won't autoconfigure addresses.

--------------------------------------------------------------------
IETF IPv6 working group mailing list
ipv6@ietf.org
Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------