[systemd-devel] Systemd setting up two Microchip switch ports as individual network interfaces and then bonding them

[Kevin P. Fleming]

While I can't comment on the specifics of configuring systemd-networkd
to use ports through DSA (although the linked GitHub issue shows that
it can be done), I really doubt you are going to be able to
successfully bond any group of such ports, because they all have the
same MAC address. In your proposed configuration, you have a NIC
connected to a switch (internal to your system), which would then have
multiple ports connected to *another* switch. Unless the switches
involved support STP or some other loop-avoidance mechanism, you will
get a switching loop in this configuration.

Connecting multiple ports between two switches requires cooperation in
the switches (STP, or LACP, or something else).

On Tue, Oct 13, 2020 at 8:56 AM Brian Hutchinson <b.hutchman at gmail.com> wrote:
>
> Hi,
>
> I have my device tree exposing two Microchip KSZ9567 switch ports.  I need to use them as individual NIC's.
>
> I've tested the DSA driver as individual nics and they work fine.  I do this with:
>
> ip addr add 192.168.0.4/24 dev lan1
> ip addr add 192.168.2.4/24 dev lan2
>
> ip link set eth0 up
> ip link set lan1 up
> ip link set lan2 up
>
> ... but I have no clue how to do this with /etc/systemd/network scripts
>
> The above was just testing/verifying my device tree and DSA driver and a step toward real goal.  Once I get two of the switch ports (the only two the hardware brings out) to act as individual NIC's my next goal is to bond them for redundancy.
>
> I really have no clue how to do that and have struggled to even uncover relevant information.  The closest thing I've found is:
>
> A discussion of DSA issues
> https://github.com/systemd/systemd/issues/7478
>
> Bonding but doesn't look like my DSA case.
> https://kerlilow.me/blog/setting-up-systemd-networkd-with-bonding/#setting-up-the-bond
>
> I tried the above link and it looked like all I did was create a switch loop as the LED's on my switch went crazy when I connected both of my ethernet ports.
>
> Anyone have experience with systemd and DSA and bonding?
>
> Regards,
>
> Brian
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