To support several use cases for Ironic bare metal deployment, we should support multiple subnet ranges for a given network. This will allow racks to have their own local layer 2 VLANs, with routing switches used to route both East-West and North-South traffic between the racks.
Some use cases where this will be a dependency:
* TripleO deployments to a routed spine-and-leaf architecture, where each rack has local VLANs and routing is used to connect the racks.
* Tenant bare metal instances in multiple provisioning subnets depending on which rack they are located.
* IP migration without recabling, where nodes are moved one-by-one to a new subnet while remaining on the same physical network.
DHCP request broadcasts are intercepted by the router and forwarded via unicast to the ironic-inspector-dnsmasq process. The IP address of the router will be inserted into the requests, and the DHCP server uses this value to determine which subnet to issue an address from. In testing, the following dnsmasq configuration worked well with multiple subnets, as long as the router for a given subnet was configured to support DHCP relay pointing to the IP address where ironic-inspector-dnsmasq is running.
dnsmasq.conf # for supporting two different subnets for provisioning
port=0
interface=br-ctlplane
bind-interfaces
dhcp-range=set:172.20.0.0,172.20.0.100,172.20.0.120,255.255.255.0,29
dhcp-range=set:172.19.0.0,172.19.0.100,172.19.0.120,255.255.255.0,29
#Options
dhcp-option=tag:172.20.0.0,option:router,172.20.0.254
dhcp-option=tag:172.19.0.0,option:router,172.19.0.254
I suspect we should move this to puppet-ironic. Leaving the inspector part incomplete for now.