[Cialug] How is this possible?

[Tom Sellers]

Zach,

Thanks for your response. What you describe is exactly what seems to be
happening.

I will check for the udev rules and see what is contained there.

I ran Windows on this machine before and never encountered this issue.



On Mon, Apr 3, 2017 at 2:03 PM, Zachary Kotlarek <zach at kotlarek.com> wrote:

> On 3 Apr 2017, at 10:44, Tom Sellers wrote:
>
> > I tried removing the added 3com card and booting with a cd version and it
> > sees the built in adapter as eth0 with 00.0c.76.be.b9.a9 as correct.  I
> > don't seem to be able to make it boot up with both adapters installed
> > without the adapters being reversed as shown in the ifconfig above.
>
>
> First I want to note that any NIC can have *any* number of IP addresses
> attached, including 0. While not the most common configuration it’s
> entirely possible to have more than one address assigned to a single
> interface; for example, you might have two logical networks — one with
> routable IPs and one with link-local IPs — on the same wire. You can also
> assign the same IP address to any number of NICs; you can have more than
> one physical wire comping into a box that you want to treat as the same
> logical network.
>
> But I don’t think any of that is what’s happening here. I think you’re
> just not getting interfaces enumerated in the order you expect.
>
> In general the order of NICs is not guaranteed to be deterministic by the
> kernel. Frequently they’ll come up in the same order because they’re
> scanned the same way at each boot, but that’s not guarantee the kernel
> makes. Even if it could make that guarantee names would still change every
> time you added or removed a NIC.
>
> Which is why udev provides a way to explicitly assign stable names to
> devices. Many distros automatically create udev configuration to ensure
> that NICs come up with the same name at every boot even if you make other
> changes to the system, and when that happened the device your system is
> calling eth0 was enumerated first, for whatever reason. Now it’s “stuck”
> that way because udev forces the name on every boot; it doesn’t happen when
> you boot from other disks because those disks don’t include the udev config.
>
> So there are two options, and you can do either or both:
> 1. Edit your udev config to assign the names you prefer
> 2. Edit your other config to use the names as assigned
>
> Also note that there’s no inherent meaning to any of the names, and you
> aren’t limited to calling them “ethX”. For example,  I have the interfaces
> with names like “uplink” using udev config like this:
>         KERNEL=="eth*", ATTR{address}=="01:23:45:67:89:ab”, NAME="uplink"
> Which I find useful because I don’t have to remember what eth4 does. The
> location of the udev rules file for NICs is distro-specific; mine is in
> /etc/udev/rules.d/00-local-rules.conf
>
>         Zach
>
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