Re: dhcpcd and multiple IPv6 gateways on one interface

[Roy Bixler <rcbixler%nyx.net@localhost>]

On Wed, Sep 13, 2017 at 06:56:51AM -0700, Andy Ruhl wrote:
> On Tue, Sep 12, 2017 at 10:37 AM, Roy Bixler <rcbixler%nyx.net@localhost> wrote:
> > I'm pretty sure that our network does not use Cisco as the router.  I
> > think that the admin. uses some kind of a Linux distribution which he
> > then sets up with an OSPF daemon and so forth.
> 
> I'll say it another way: Once you put an IPv6 address onto some
> devices, Cisco in particular, they "just decide" to become a router
> and do router advertisements. This is probably the case on your
> network.

I don't know of any Linux distribution that would try to "just decide"
to "become a router".  Perhaps there's some niche distribution which
claims to "make routing easy", but I doubt that's the case here.  The
network admin. dislikes appliances and prefers Gentoo which, if
anything, is very much a DIY distro.

> So really, you have 2 issues here:
> 
> 1. Who is sending out router advertisements? You can probably find
> that out easily enough since the MAC is embedded in these link local
> addresses. Might want to find out if those machines should be doing
> that. Probably not.

I don't know the answer, because I haven't set up this network.

> 2. How does a machine properly handle this situation? Linux seems to
> just put in equal cost routes for all of them, so either they are load
> balancing or they have some other selection criteria. Based on the
> behavior of machines doing router advertisements, I would hope that
> reachability is being done somehow, but maybe this is wishful
> thinking. (Again, unresearched.)

A bit more research shows that this is a Linux-specific feature.
There is a suite called "iproute2" which does this.  You can find more
information here:

https://wiki.linuxfoundation.org/networking/iproute2

-- 
Roy Bixler <rcbixler%nyx.net@localhost>
"The fundamental principle of science, the definition almost, is this: the
sole test of the validity of any idea is experiment."
-- Richard P. Feynman