Host deploys with the wrong VLAN

[Mike Pontillo]

Hi William,

On Thu, Feb 8, 2018 at 3:58 PM, William Edwards <william at williamedwards.io>
wrote:
>
> I have been experiencing problems where, upon deploying an Ubuntu node,
> the network configuration of the node changes after the install, and
> becomes inaccessible. Adding and commissioning the node in MaaS works
> perfectly fine, and even the install log is reported back to the MaaSserver.
> Before deploying the node, I selected one of our VLANs (VLAN 11) and set it
> to use DHCP, but after the install, the network configuration reflected in
> the web UI changes to VLAN 10 after the installation completes.
>
> I currently have a rack controller on VLAN 10, with DHCP & DNS disabled,
> so it can be handled by an external service, and our our DHCP service is
> configured to allow machines to PXE boot off of the rack controller in VLAN
> 10. The PXE booting across VLANs itself works perfectly fine.
>

I just ran into this myself a week or two ago. I think this is occurring
because MAAS formally supports two boot methods:

 - MAAS-managed DHCP
 - DHCP relay (a.k.a. "ip helper-address"); in other words, forwarding the
entire DHCP packet to MAAS

MAAS really prefers to manage the DHCP server directly, so that it can
manage HA for DHCP and provide all the static leases it knows about.

What you are doing sounds like instructing your existing DHCP server to PXE
boot from MAAS. MAAS can work in this scenario (and I know that some people
have done this successfully in their environment), but MAAS wasn't designed
to work this way.


> If I deploy a node on the same VLAN that the rack controller is on,
> everything works as expected.
>
> Is this a bug? Shouldn't it be possible to deploy a node from rack
> controllers in different VLANs?
>

Arguably it's a feature request[1], but you might be able to work around
the problem if you tell MAAS that VLAN 11 is relaying its DHCP requests to
VLAN 10. Then when the machine PXE boots, MAAS won't reset the VLAN to the
same VLAN it observed the boot coming from on the rack controller. Simply
browse to VLAN 11 in the MAAS UI, select "Relay DHCP", and select VLAN 10
as the destination.

Please let me know if that works for you!

Regards,
Mike

[1]: Though for the record, I think the code that is doing this is in in
maasserver/rpc/boot.py::get_config(), which is where we reconcile PXE
requests on the server.
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