On Tue 23 Jan 2018 at 13:41:31 (+0000), Joe wrote:
> On Tue, 23 Jan 2018 11:12:41 +0000 (UTC)
> Curt <cu...@free.fr> wrote:
>
> > On 2018-01-23, Andy Hawkins <a...@gently.org.uk> wrote:
> > > Hi,
> > > In article <20180122185135.GA12212@alum>,
> > > David Wright<deb...@lionunicorn.co.uk> wrote:
> > >>> You should be able to do that with IPv4 too. If DHCP address
> > >>> allocation fails,
> > >>
> > >> Elaborate on this please. What do you mean by "fails".
> > >> What am I meant to want to fail?
> > >
> > > If a host that's expecting to receive its address via DHCP receives
> > > no response from the DHCP server, it should fall back automatically
> > > to a 'link local' address.
> >
> > Is this what you're referring to ("an IPv4 address within the
> > 169.254/16 prefix that is valid for communication with other devices
> > connected to the same physical (or logical) link," failing--or in the
> > absence of--automatic or manual assignment)?
> >
> > https://tools.ietf.org/html/rfc3927
>
> Indeed so. It ensures that if the DHCP server temporarily suffers a
> problem, any Windows machine on the network (I have no data for Linux)
> that gets rebooted stands absolutely zero chance of communicating with
> any network machine which hasn't been rebooted. The idea that the
> previous working address (even within the lease period), or the
> [Windows] manually entered 'alternate' address should be tried does not
> arise.
>
> I would hope that the Linux network management utilities take a more
> intelligent view of the situation, I haven't yet had cause to find out.
This would all be a step in the wrong direction here. Point (2) was
that using IPv6 over CAT5 avoids swamping the router. (Of course,
that's already been snipped out of the thread.) If the DHCP server
is down, then the router is down, and there are no links to anywhere
except the CAT5 cable I've just connected.
So why would I worry about whether the IPv4 had reconfigured itself
when I've got a perfectly good dedicated IPv6 link between the two
computers? And why should I be worrying about DHCP failures?—the
only time my router is dead is during power cuts.
Cheers,
David.
