SLAAC(autoconfig) vs DHCPv6
Iljitsch van Beijnum
iljitsch at muada.com
Mon Aug 18 16:11:16 CDT 2008
On 18 aug 2008, at 22:23, Dale W. Carder wrote:
> - really, really, really broken: it didn't support handing out
> any DNS info until RFC 5006, thus SLAAC still requires human
> intervention on a client to make "teh v6 interwebs" work.
While I agree that it is bad that the DNS configuration issue took so
long to fix, I wouldn't consider this a flaw of stateless
autoconfiguration, which works extremely well. There have been many
times that I was at conferences where the IPv4 DHCP wouldn't work so
it was impossible to go online, while stateless autoconfig rarely
creates any problems. (Although there could be connectivity problems
> - doesn't ship w/ some OS's
Forget about it on XP, but it's in Vista. You can add it to BSD/Linux
without too much trouble (are there good, bugfree implementations for
those yet?) but Mac is a problem for prospective DHCPv6 users because
the network configuration mechanisms are fairly proprietary and DHCPv6
isn't likely to be supported any time soon.
> - new (danger code), not all features implemented
> - router support for dhcpv6 relay very limited
> - advanced things like prefix delegation don't really seem to
> have been ironed out.
Actually the prefix delegation has worked just fine for me. This is
the redeeming feature in DHCPv6.
In my opinion, DHCPv6 was severely misdesigned. For instance, there
are stateful and stateless variations, and the _client_ has to choose
which to use. DHCPv6 also doesn't give you a subnet prefix length or a
default gateway, so you still need router advertisements (that are
also used for stateless autoconfig). The latter can be considered a
feature, but I'm guessing the lack of a subnet prefix other than the
assumption that the whole world uses /64 has been giving DHCPv6 server
implementers a lot of headaches.
> In case you weren't confused enough between the two, they are not
> mutually exclusive. You can run both SLAAC and DHCPv6 at the same
> time on the same L2.
Of course there's no telling what exactly the clients are going to do
in that case...
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