[openstack-dev] [quantum] RFC: quantum baremetal config/work to do

Robert Collins robertc at robertcollins.net
Wed Jan 9 03:15:46 UTC 2013

On 7 January 2013 23:01, Gary Kotton <gkotton at redhat.com> wrote:
> On 01/06/2013 09:42 PM, Robert Collins wrote:
>> Hey, so I've been poking at quantum with the baremetal hypervisor on
>> classic l2 switches - no openflow.
>> Here is what I think needs to be done to make it all work, and what I
>> think 'it' is :)
>> So the goal is to have a regular L2 network, with quantum + baremetal
>> nova managing dhcp on it.
> Why have Nova managing the DHCP. Quantum has IPAM and a option of using a
> DHCP agent. The advantage of this is that the DHCP agent will only allocate
> IP addresses for devices that are registered as Quantum ports.

I phrased that badly. I mean 'quantum + baremetal nova' as an
aggregate, not that nova would do DHCP. In fact, the point of this is
to stop nova doing DHCP, though it still needs to orchestrate the
*TFTP* aspects of it.

Specifically, I want the dnsmasq opts file to look like this:

Where novabaremetalhostname2 is the nova compute host that is doing
baremetal (and there may be many such, though commonly it will be 2
for HA).

And the host file will contain:
To trigger 52:54:00:97:71:c3 to TFTP boot from tftp-host.novabaremetalhostname2

Once that it setup, until that baremetal host is taken out of
rotation, its all static.

>> Ignoring quantum for the moment, what needs to happen is that:
>>   - machines attempt PXE booting using their own MAC address
>>   - if the machine is not known to nova, something sensible (e.g.
>> allocate from a pool, or log and ditch, or allocate a number and do
>> hardware discovery)
>>   - if the machine is known to nova, boot it providing appropriate
>> bootfile-name, server-ip-address and tftp-server options.
>>   - nova's baremetal hypervisor then handles tftp and the rest of the
>> boot process.
>> What I have so far is this:
>>   - quantum with the ovs plugin
>>   - with a provider network configured (e.g.
>> tenant_network_type=none
>> network_vlan_ranges=ctlplane
>> bridge_mappings=ctlplane:br-ctlplane
>> and a network and subnet made with that:
>> $ quantum net-create ctlplane --tenant-id $tenantuuid
>> --provider:network_type flat --provider:physical_network ctlplane
>> $ subnet-create --ip-version 4 --allocation-pool
>> start=,end= --gateway= $netuuid
>> Will answer DHCP for DHCP requests coming from the physical L2 network
>> if the MAC has been registered as a port.
>> My plan for unknown machines for now is to ignore them (can just have
>> a deliberately slow DHCP server running on the same network, as a
>> stopgap), but long term would like to teach quantum a fallback
>> configuration for unknown requests. [which might be to proxy-DHCP the
>> request].
> The Quantum DHCP agent will only provide IP's for MAC addresses that are
> known to the agent.

Today for sure. Would you be opposed to changing that (when
configured)? The idea is to be able to inventory a rack by turning it
on, rather than by doing manual data entry. We would TFTP boot a
nondestructive ramdisk on every machine, which would report back to an

> When you create a Quantum port you are able to specify the MAC address of
> the port. This may require a few tweaks to the Nova code when creating the
> Quantum port. Today you are able to do a nova boot and pass the port id a
> parameter. So if you create the Quantum port outside of Nova then you can do
> this with the existing API's.

Thanks, this kindof works. I found two things were odd: firstly, the
port is deleted when the instance is, so you have to create it every
time. Secondly, as there is no baremetal way to boot a specific
baremetal node, you can only do this with one unprovisioned bare metal
node at a time - its clearly the right path for the baremetal compute
code to drive things, but its not something users can do sensibly by

 - manual mac address stuff needs no quantum changes AFAICT
 - the TFTP boot configuration I describe above does need changes. I
was thinking of this model:
   - have a TFTP server object
   - that gets mapped onto a subnet
   - and individual ports are able to be set 'boot off <this tftp server>'
   - its up to nova to tell quantum if the set of baremetal boot
machines changes, to update configs.

Thoughts (and pointers to where in the code to start changing things)


Robert Collins <rbtcollins at hp.com>
Distinguished Technologist
HP Cloud Services

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