Re: DHCP fall back to link-local? (IPv4)

[Dan Williams <dcbw redhat com>]

On Thu, 2009-04-16 at 07:29 +0100, Roy Marples wrote:
> Marc Herbert wrote:
> > As an alternative solution, maybe I could try to have dhclient (instead
> > of NetworkManager) execute avahi-autoipd ? This would require increasing
> > the timeout in NetworkManager higher than the one in dhclient, do you
> > think this is feasible?
> 
> NM supports dhcpcd-4.x and better, which in turn supports ZeroConf. NM
> explicitly disables dhcpcd ZeroConf support via a command line switch.
> Remove this switch in the NM source and you get this behaviour.

The problem is that most of the time this isn't useful.  Either you have
a DHCP server and you can get to external resources, or you don't have a
DHCP server and you just want to talk to another computer.  If you have
a DHCP server, but it's down, falling back to IPv4LL doesn't get you
anywhere.  If you don't have a DHCP server, and you know that, then
making NM use DHCP is also pointless, because you've just added about 45
seconds of latency to the connection.

I guess my point is that in the DHCP case, fallback to zeroconf is
simply confusing for a ton of users (which is why that behavior was
removed in the first place) and not useful for getting to external
resources.

So if you know you want zeroconf, use zeroconf, don't use DHCP.

Dan

> DHCP
> DHCP
> timeout
> ZEROCONF
> DHCP
> DHCP
> ...
> ASSIGNED DHCP
> DROP ZERCONF
> 
> It also defends it's IPv4LL address.
> 
> Because of the way ZeroConf is designed to work, putting the work into
> the DHCP client makes perfect sense :)
> 
> If your distro doesn't ship dhcpcd-4, you can get the source from here
> http://roy.marples.name/projects/dhcpcd
> 
> Thanks
> 
> Roy
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