v6 & DSL / Cable modems [was: Private use of non-RFC1918 IP space (IPv6-MW)]
nanog at daork.net
Tue Feb 10 16:38:59 CST 2009
On 11/02/2009, at 10:41 AM, Ricky Beam wrote:
> It's useless. It does NOT provide enough information alone for a
> host to function. In your own words, you need a DNS server. That
> is NOT provided by RA thus requires yet another system to get that
> bit of configuration to the host -- either entered manually, DHCPv6,
> or from IPv4 network configuration (ie. DHCP!) Forcing this BS on
> the world is a colossal waste. We've had a system to provide *ALL*
> the information a host needs or wants in the IPv4 world for years.
> Why it's not good enough for IPv6 is beyond me.
You are correct, alone RA does not provide enough for a host to
We have two mechanisms of providing addressing information to hosts -
SLAAC and DHCPv6.
How do you, as a network manager, tell hosts which one to use? RA
performs this function. Without RA you need to go around all the
machines and manually configure how they will discover what addresses
to use. That seems a bit silly, and going around every machine is
something you have already indicated you don't want to do.
RA has two functions - telling your hosts which of SLAAC and DHCPv6 to
use for addressing information, and providing addressing information
in the case of SLAAC. Also, in the case of SLAAC, it might hint to the
client to get additional information from DHCPv6 - DNS servers and so
on - in this case it will not get addressing information.
Perhaps you have a problem with SLAAC? That is fine, you might not
want to use it. Other people *do* want to use it, and RA is the best
place to signal which of SLAAC and DHCPv6 a host should use for
Please do not use blanket comments that RA is bad if you actually mean
SLAAC. Yes, if we do not have SLAAC then we don't need RA, because
hosts will always know to use DHCPv6. However, many people do want
SLAAC, so we need RA.
If you have an idea for alternative to RA for indicating whether to
use SLAAC or DHCPv6 then I encourage you to get involved in the IETF
and get your idea written up. If you would like to deprecate/fix SLAAC
because you have a problem with it then again, I encourage you to get
involved in the IETF.
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