Subject: RE: [dhcwg] DAD in DHCPv6.

From: [email-masked]
Date: Sat, 24 Sep 2005 00:22:19 -0400

Actually, the 'M' bit has nothing to do with stateless.

It is the 'A' bit in a Prefix Information Option in the RA:

      A              1-bit autonomous address-configuration flag.  When
                     set indicates that this prefix can be used for
                     autonomous address configuration as specified in
                     [ADDRCONF].

As Ralph already pointed out, RFC 3315 strongly suggests (SHOULD) that
clients do DAD. It is also one of the reasons we have a DECLINE message
-- a client may find that an address is already in use and therefore
should notify the DHCP server of that fact so the address can be taken
out of circulation.

- Bernie

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] 
> On Behalf Of Ted Lemon
> Sent: Saturday, September 24, 2005 12:02 AM
> To: Andrea G Forte
> Cc: [email-masked]
> Subject: Re: [dhcwg] DAD in DHCPv6.
> 
> On Sep 23, 2005, at 1:01 PM, Andrea G Forte wrote:
> > I have a question about DHCPv6 and the statefull address  
> > configuration. It seems that DAD is performed only in the 
> stateless  
> > procedure and no DAD at all is performed in the stateful 
> procedure.  
> > How can the DHCP server be sure that the IP address that is going  
> > to assign has not been manually configured by someone other 
> client?  
> > (Which is the reason for having DAD in DHCPv4).
> 
> Nodes are not supposed to do stateless autoconf using prefixes that  
> are managed (that is, prefixes announced in router advertisements  
> where the 'M' bit is set).
> 
> Unfortunately, every IPv6 implementation I've seen so far except  
> Solaris ignores the 'M' bit entirely, so you are right to be 
> concerned.
> 
> 
> 
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