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Re: network unrachable problem

Tony van der Hoff wrote:
> Certainly, with eth0 unplugged, ifconfig shows it to be still up, and ip
> route show shows both interfaces, so that's very likely the cause.

Sounds like the problem.  Because I am pretty sure that ifplugd has
been given the responsibility to monitor the link status and to bring
the interface up and down appropriately.  If that isn't working then
these kinds of problems will arise.

A couple of hints that may help.  It is okay to have multiple default
routes.  They are used in priority order.  If you have two interfaces
and both are using dhcp then both will get a default route.  (Normally
when configuring static interfaces only one is assigned a default
route.)  The last one configured will be the default route used.  When
an interface is downed a default route associated with it will be
removed from the route table.  Being removed the next available
default route would then become active.

The Linux kernel changed the display order for routes.  In Squeeze the
Linux kernel displays the order is the traditional order with the
priority display listing from top to bottom and the first matching
route wins.  In Wheezy the Linux kernel reverses this display order
and it is from bottom to top instead of top to bottom.  I consider
this a bug although I am sure someone did it intentionally.  The
difference between kernel versions is definitely annoying.

> However, ifplugd is running, as shown by ps; an instance for each
> interface. My /etc/default/ifplugd is identical to yours.

I should say that on my only Pi system at the moment I have been
hacking on it severely.  I have been playing with the bonding
interface and so poking around in this area.  I have deviated from
the-stock-install quite a few places in the process during my
experiments.  So I probably no longer have a good match to what you
see on your system.  So the works-for-me statement about this may be
due to my modifications.  Sorry.  I am going to be setting up a
pristine Pi here in a day or so and that will give me an opportunity
to recreate the stock setup.  I am sure I will run into your problem

> If I manually pull down eth0, and then restore the cable, then it comes
> up automatically.
> Digging around in /etc/udev, I find it is practically empty; is udev
> still the way devices are detected?

Yes.  And I also noticed but had not investigated yet that
70-persistent-net.rules isn't being created.  But I was thinking it
was probably something broken on my system.  But it could be an early
init script that is actively removing or avoiding it due to the way
the Pi is designed to be used.  This is causing me problems due to my
Pi having three network interfaces but I assumed it was something I
caused on my system.  But I guess not.


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