The topic of subnet management pertains to whether MAAS is in full control of a subnet or not. When a subnet is managed, all aspects of IP address allocation are handled by MAAS. This includes DHCP leases and assigned static addresses. Typically MAAS would have one managed subnet, but any additional subnets can be unmanaged. This allows for more control over which subnet gets used for DHCP and which ones do not. Additionally, as detailed below, an unmanaged subnet treats reserved IP ranges differently, and in a way that some administrators find more intuitive.
When management is enabled for a subnet, MAAS will:
- Lease addresses for DHCP from a reserved dynamic IP range
- Assign static addresses not included in a reserved IP range, typically via 'Auto assign' IP allocation mode for a node.
When management is disabled for a subnet, the definition of a reserved IP range differs from the managed mode. Here, a reserved IP range tells MAAS to only allocate addresses from this range (via 'Auto assign'). In addition, DHCP will never lease addresses from an unmanaged subnet.
By default, a subnet is managed, but it is easy to change this.
To disable (or re-enable) subnet management navigate to the 'Subnets' page and select the subnet. There is a slide switch labelled 'Managed allocation'. Click the label (or the switch icon itself) to toggle between enabled (dark blue) and disabled (grey).
See MAAS CLI for how to do this with the CLI.
MAAS will keep track of all assigned addresses, regardless of whether they come from managed or unmanaged subnets.