> and so the exchange should fail at this stage.
I just realised some implications of your post. As I wrote in my other
mail, the client indeed does not need to send IA options and hence the
NoAddrsAvail will not be sent to the client in an Advertise message, if
no IA options are used in the first place. 

But the real question is: does the client actually know when it doesn't
need to send IA options? Consider this scenario:

- O bit is set in RAs
- DHCPv6 server is configured _not_ to assign addresses to DHCPv6 
  clients (SAA is used)
- there is a DHCPv6 client that DOES NOT respect the O bit and
  consequently will request an address from the DHCPv6 server next
  to information options (DNS, etc.)

In this case, the client doesn't know that it doesn't actually need to
request an address and it will use IA options consequently. Hence the
retrieval of information options will fail for the reasons you
identified. That is, needless to say, bad. The only way around it is to
either beforehand configure the client not to be a stateful DHCPv6
client or to only use a DHCPv6 client that respects the O bit. On the
other hand, if you by default configured stateless DHCPv6 you would be
lost in a subnet without RAs. So, the only way out of this dilemma is to
have a DHCPv6 client that respects the M/O bits.

Christian


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