Okay “I lied too many people” is a little harsh. I didn’t know better and repeated what I had read else where. And I repeated it in many talks, workshops or consulting gigs. And I know several other people who repeted the same thing. Here is what I told people

The use of DHCPv6 is steared via router advertisments.

Router advertisments( (RA) are defined in RFC4861. There are two flags regarding DHCPv6.

  • M - which indicates that a client can get an address via DHCPv6.
  • O - which indicates that a client can get other information (DNS resolver, search domain, …) via DHCPv6.

But a client can do DHCPv6 request regardles of what the RA is telling. I only new that from MS Windows and put that away as okay, it’s MS. But then I watched an Ubuntu VM booting while running Wireshark. DHCPv6 requests during boot.

So I started re-reading RFCs. And yes, an RA gives a hint to the client OS. The client can do DHCPv6 without the flags in the RA.

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