[IRONIC] - Various questions around network features.

Julia Kreger juliaashleykreger at gmail.com
Mon Jul 11 22:13:14 UTC 2022

Greetings! Hopefully these answers help!

On Sun, Jul 10, 2022 at 4:35 PM Gaël THEROND <gael.therond at bitswalk.com> wrote:
> I everyone, I’m currently working back again with Ironic and it’s amazing!
> However, during our demo session to our users few questions arise.
> We’re currently deploying nodes using a private vlan that can’t be reached from outside of the Openstack network fabric (vlan 101 - and everything is fine with this provisioning network as our ToR switch all know about it and other Control plan VLANs such as the internal APIs VLAN which allow the IPA Ramdisk to correctly and seamlessly be able to contact the internal IRONIC APIs.

Nice, I've had my lab configured like this in the past.

> (When you declare a port as a trunk allowed all vlan on a aruba switch it seems it automatically analyse the CIDR your host try to reach from your VLAN and route everything to the corresponding VLAN that match the destination IP).

Ugh, that... could be fun :\

> So know, I still get few tiny issues:
> 1°/- When I spawn a nova instance on a ironic host that is set to use flat network (From horizon as a user), why does the nova wizard still ask for a neutron network if it’s not set on the provisioned host by the IPA ramdisk right after the whole disk image copy? Is that some missing development on horizon or did I missed something?

Horizon just is not aware... and you can actually have entirely
different DHCP pools on the same flat network, so that neutron network
is intended for the instance's addressing to utilize.

Ironic does just ask from an allocation from a provisioning network,
which can and *should* be a different network than the tenant network.

> 2°/- In a flat network layout deployment using direct deploy scenario for images, am I still supposed to create a ironic provisioning network in neutron?
> From my understanding (and actually my tests) we don’t, as any host booting on the provisioning vlan will catch up an IP and initiate the bootp sequence as the dnsmasq is just set to do that and provide the IPA ramdisk, but it’s a bit confusing as many documentation explicitly require for this network to exist on neutron.

Yes. Direct is short hand for "Copy it over the network and write it
directly to disk". It still needs an IP address on the provisioning
network (think, subnet instead of distinct L2 broadcast domain).

When you ask nova for an instance, it sends over what the machine
should use as a "VIF" (neutron port), however that is never actually
bound configuration wise into neutron until after the deployment

It *could* be that your neutron config is such that it just works
anyway, but I suspect upstream contributors would be a bit confused if
you reported an issue and had no provisioning network defined.

> 3°/- My whole Openstack network setup is using Openvswitch and vxlan tunnels on top of a spine/leaf architecture using aruba CX8360 switches (for both spine and leafs), am I required to use either the networking-generic-switch driver or a vendor neutron driver ? If that’s right, how will this driver be able to instruct the switch to assign the host port the correct openvswitch vlan id and register the correct vxlan to openvswitch from this port? I mean, ok neutron know the vxlan and openvswitch the tunnel vlan id/interface but what is the glue of all that?

If your happy with flat networks, no.

If you want tenant isolation networking wise, yes.

NGS and Baremetal Port aware/enabled Neutron ML2 drivers take the port
level local link configuration (well, Ironic includes the port
information (local link connection, physical network, and some other
details) to Neutron with the port binding request.

Those ML2 drivers, then either request the switch configuration be
updated, or take locally configured credentials to modify port
configuration in Neutron, and logs into the switch to toggle the
access port's configuration which the baremetal node is attached to.

Generally, they are not vxlan network aware, and at least with
networking-generic-switch vlan ID numbers are expected and allocated
via neutron.

Sort of like the software is logging into the switch and running
something along the lines of "conf t;int gi0/21;switchport mode
access;switchport access vlan 391 ; wri mem"

> 4°/- I’ve successfully used openstack cloud oriented CentOS and debian images or snapshot of VMs to provision my hosts, this is an awesome feature, but I’m wondering if there is a way to let those host cloud-init instance to request for neutron metadata endpoint?

Generally yes, you *can* use network attached metadata with neutron
*as long as* your switches know to direct the traffic for the metadata
IP to the Neutron metadata service(s).

We know of operators who ahve done it without issues, but often that
additional switch configured route is not always the best hting.
Generally we recommend enabling and using configuration drives, so the
metadata is able to be picked up by cloud-init.

> I was a bit surprised about the ironic networking part as I was expecting the IPA ramdisk to at least be able to set the host os with the appropriate network configuration file for whole disk images that do not use encryption by injecting those information from the neutron api into the host disk while mounted (right after the image dd).

IPA has no knowledge of how to modify the host OS in this regard.
modifying the host OS has generally been something the ironic
community has avoided since it is not exactly cloudy to have to do so.
Generally most clouds are running with DHCP, so as long as that is
enabled and configured, things should generally "just work".

Hopefully that provides a little more context. Nothing prevents you
from writing your own hardware manager that does exactly this, for
what it is worth.

> All in all I really like the ironic approach of the baremetal provisioning process, and I’m pretty sure that I’m just missing a bit of understanding of the networking part but it’s really the most confusing part of it to me as I feel like if there is a missing link in between neutron and the host HW or the switches.

Thanks! It is definitely one of the more complex parts given there are
many moving parts, and everyone wants (or needs) to have their
networking configured just a little differently.

Hopefully I've kind of put some of the details out there, if you need
more information, please feel free to reach out, and also please feel
free to ask questions in #openstack-ironic on irc.oftc.net.

> Thanks a lot anyone that will take time to explain me this :-)


More information about the openstack-discuss mailing list