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Re: systemd network interface configuration (was "Re: systemd woes continue")

On Thu, Sep 19, 2019 at 09:10:20AM +0200, John Paul Adrian Glaubitz wrote:
> (...)
> So, can you please type "ip a" and check what device name is actually assigned
> to your wired card and if it differs from "eth0", adjust your /etc/network/
> interfaces file?
> If your wired card is actually named "eth0", then the problem is somewhere
> else and we need to proceed in your next mail.

The wired card really *is* "eth0".  "ip a" shows five interfaces in the
current active (correct) environment:

1: lo
2: eth0 (my primary network interface, connected to a pre-CIDR routable
        class C network)
3: enx00e04c6881f7 (USB NIC connected to an internal non-routable class
                   C network)
4: sit0@NONE (tunnel for IPv6-in-IPv4 traffic)
7: he-ipv6@NONE (a point-to-point IPv4 connection to the IPv6 tunnel broker)

The wireless interface in the "interfaces" file corresponds to a USB
adapter I haven't used with the Alpha in a long time.  I left the
configuration info there as a reminder of how to do that if/when it
becomes necessary :-).

At the risk of providing too much information, the Alpha is serving as a
local IPv6 gateway router.  "/etc/sysctl.conf" has
"net.ipv6.conf.all.forwarding=1" which is appropriate (required) for a
router, because otherwise, "radvd" will "unexpectedly" configure an
additional global IPv6 address for "eth0" which you definitely do not
want.  The only global scope IPv6 addresses are statically assigned to
the "eth0" and "he-ipv6" interfaces.

There remains a bit of strangeness, even if/when the interfaces are
brought up correctly, because of the "gateway" configuration line
associated with the USB interface.  I need to comment that out: multiple
default routes at identical priorities is a legitimate configuration
error in my setup.  At one time, there was a legitimate reason for that
gateway line to be there: no need to go into that level of detail at
present :-).


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