Static vs SLAAC - Static expected to be preferred?

[Geert Hendrickx]

On Wed, May 04, 2011 at 22:41:10 +0930, Mark Smith wrote:
> This last half dozen emails or so, showing the significant amounts of
> effort involved in disabling or overriding SLAAC addresses, are exactly
> why I think configuring static addresses should be no harder than 
> 
> ip -6 addr add 2001:db8::1/64 dev eth0
> 
> as it is in IPv4. If the host has automatically learned SLAAC addresses,
> you've inherently chosen to override them by the action of manually
> configuring a static. The SLAAC addresses won't do any harm if they're
> left there and never used as source addresses, and you still get to keep
> using RAs for their other purposes.
> 
> A simplistic approach would be to just blindly prefer statics over all
> other types of addresses. However, I think the more flexible approach is
> to have the current value of the preferred lifetime value used as the
> deciding factor. Static addresses, with their default infinite preferred
> lifetimes, would always win. If you wanted to have a static
> address only used for incoming connections (i.e. as a incoming
> destination address for a server process), but use SLAAC (or other)
> addresses for outgoing connections, you'd set the static address
> preferred lifetime to 0, and leave it's valid lifetime as infinity.



I fully agree with this.  This appears to me the simplest and most predictable
way to configure static vs dynamic IPv6, and allows for all different options
and use cases mentioned.

The current Linux implementation where "last added address wins", disregarding
the *preferred* lifetime, is just annoying.


	Geert


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