RA & DHCP problem...

[S.P.Zeidler]

Thus wrote Tarko Tikan (tarko at lanparty.ee):

> >In other words: create undefined behaviour that breaks in new and exciting
> >ways for every operating system (version) around.
> 
> No, it's not really different from having unexpired RAs around or
> manually adding two IPs to an interface. These situations already
> happen and operating systems deal with them.

Many host operating systems network stacks expect to have exactly one
default route. (If you have more than one, which is the default?) 
This is not connected to the question of how many IP addresses they have
configured on whichever many interfaces. This is the question "if I have
conflicting information from DHCP and RA, where should the packets go",
and there is no immediately obvious answer to that question.

> >Thus creating a situation where instead of DHCP "and" RA, you get an
> >"exclusive or" to preserve your sanity. You might as well declare RA
> >deprecated directly.
> 
> There is no need to deprecate RA at all. It is good for many
> usecases but not for IA_PD unfortunately.

-If- there get to be DHCP v6 routing options -and- there is no clear
guidance what to do when DHCP and RA conflict, sooner rather than later
best practise will be not to run DHCP and RA on the same network, because
information will disagree often enough if you give it any chance at all to
do so.

My personal guess is that this would mean that RA would vanish due to lack
of use. Too many people are familiar with DHCP in v4 to not just translate
their setups 1:1 with longer adresses if they get half a chance.

Note this is not an argument against or for routing options for IPv6 in
DHCP; it's just an argument against declaring it Someone Elses Problem
how to handle conflicting information if that way gets chosen.
I have the suspicion I would wind up being Someone Else in this case,
and would rather not be happy with the results :-P

regards,
	spz
-- 
spz at serpens.de (S.P.Zeidler)