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

[Eloy Paris <peloy chapus net>]

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.

[...]

> > For this to work, do I need a userspace daemon that processes these
> > router advertisement messages?
>
> That deamon to do RA in userspace is NetworkManager.

Okay, thanks for the insight. Yes, things do work now that I went with
"Automatic" configuration albeit with a delay of a couple of minutes
until I have full connectivity.

> Also make sure that the connection is not never-default (by default it
> is never-default=no):
>
>   nmcli connection show $CON_NAME | grep ipv6.never-default

Yes, that was not set.

> Also note, you can configure the ipv6.gateway property manually too.

Right, I figured, but that would cause problems as I move from network
to network so I was trying to get this to work with automatic
configuration.

In any case, changing from "Automatic, DHCP only" to "Automatic" did the
trick; thanks! I can live with the delay that I am seeing.

Cheers,

Eloy Paris.-