DHCPv6 and MAC Address inclusion

sthaug at nethelp.no sthaug at nethelp.no
Wed Jan 25 09:58:52 UTC 2012


> > So let's assume I'm a DHCPv6 server, and I receive the following three
> > Solicit messages (all from the same client since they have the same
> > DUID):
> > 
> > 1. (DUID1, IAID2)
> > 2. (DUID1, IAID3)
> > 3. (DUID1, IAID4)
> > 
> > Furthermore, assume the two first Solicit messages are sent through
> > Ethernet interface 1, and the last Solicit message is sent through
> > Ethernet interface 2.
> > 
> > How can the server differentiate the client interfaces?
> 
> It would assume that there are three interfaces, not two.   That's the point of the IAID.   However, typically a client would not do this-it would only send one IAID for each interface.   You'd have to specially configure it to send more.

I'm afraid I have to conclude from this that IAID cannot be reliably
used to differentiate client interfaces. Especially since RFC 3315
describes Identity association (IA) this way (p. 11):

"A collection of addresses assigned to a client.  Each IA has an
associated IAID.  A client may have more than one IA assigned to it;
for example, one for each of its interfaces."

I see nothing here which prevents a client from having several IAs for
one interface. I agree that this may be unusual - however, given the
wide spread of clients out there I have a hard time depending on only
one IA per interface.

Steinar Haug, Nethelp consulting, sthaug at nethelp.no



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