Re: IPv6 with DHCP -- how is default route set?

[Josef Bacik <jbacik fb com>]

On 10/20/2015 12:37 PM, Eloy Paris wrote:
> Hi Thomas,
>
> Thanks for the response. A few comments below (inline)...
>
> On Tue, Oct 20, 2015 at 06:20:21PM +0200, Thomas Haller wrote:
>
> > On Tue, 2015-10-20 at 11:29 -0400, Eloy Paris wrote:
> > > Hello,
> > >
> > > The company I work for has an IPv6-enabled network that requires
> > > configuration via DHCP. I get assigned a global IPv6 address just
> > > fine
> > > after configuring the NetworkManager entry for my NIC with
> > > "Automatic,
> > > DHCP only".
> >
> >
> > Usually, the default gateway comes via the Router-Advertisements.
> >
> >
> > I would rather expect that you choose
> >
> >    "Automatic",
> >
> > which will use RA + DHCP6 (if the RouterAdvertisements indicate to use
> > DHCP).
> >
> > "Automatic, DHCP only" will not use RA at all.
>
> I see. I had been using "Automatic, DHCP only" because I thought that
> when using "Automatic" nothing happened (no global IP address was
> obtained). However, I just tried and it worked, and a default IPv6 route
> was even installed.
>
> I realize now that it is not that nothing happened but that things took
> a long time (a couple of minutes) to happen -- first, there was a delay
> to get an IPv6 address, and then there was a delay (after the interface
> had a global IPv6 address) to see the default route installed.
>
> Are these delays normal; do they depend on the frequency of router
> advertisements? If so, can NM not elicit a router advertisements by
> sending a router solicitation? If that is what is supposed to happen
> then I don't understand the delays. In contrast, IPv4 configuration is
> immediate.

Part of the problem is NM groups together route discovery and SLAAC, 
this makes it unusable for us in our ipv6 only clusters.  I'm in the 
process of fixing this now so you can still have proper route discovery 
and use dhcpv6 or static addressing and then you'll get the immediate 
ipv6 configuration.  Thanks,

Josef