Re: Support for direct connection without cross cable

[Dan Williams <dcbw redhat com>]

On Sat, 2011-10-08 at 21:18 +0700, Arief M Utama wrote:
> Hi all,
> 
> 
> I'm just wondering, and might as well send the message on the list, in
> case someone has more ideas.
> 
> On recent windows, with recent network cards, I noticed (on a couple
> laptops) that windows can setup networking to a direct-connected to
> another device (tested couple of times with network-drives, such as WD
> MyBook World) with simple straight forward ethernet cable. No crossing
> needed.
> 
> I'm wondering if NM (or linux?) can support this as well?

Most network cards have supported direct vs. crossover detection for a
while, so that shouldn't be a problem.  What likely happens here is that
when DHCP fails, the OS assigns a IPv4 Link-Local address, which
presumably the network drive also does, and they can talk on a LL
network.  We used to have automatic functionality like that in NM, but
people got really confused as to why NM said they were connected to the
Internet when they really weren't.  But that was long ago and we could
probably figure out a better behavior here.  As in, really, this should
only happen on wired networks, and even after assigning a LL address we
should periodically retry DHCP just in case you're connected to a real
network but the DHCP server went down for 5 minutes.  Something like
that.  But currently it's not automatic since doing this breaks a bunch
of other use-cases.

Dan