An asterisk * in the title indicates the field is mandatory.
If a field has a default value, it is shown in the Description column.
If the field type is an array, the Field Name has a .[n] suffix, where n is the array index placeholder.
Object and array field names are listed to provide context. If a field belongs to an object or an array, the full field name is shown in dot separated notation.

Title	Description	Details
Description	A description of the subnet being created.	Field Name: Description Type: String
Element		Field Name: Element Type: String
InMemory	Creates an object reference without actually committing the object as a permanent change. If you assign the output of this cmdlet called with this parameter to a variable, you can make changes to the properties of the object reference and then commit those changes by calling this cmdlet's matching Set-<cmdlet>.	Field Name: InMemory Type: Boolean
MaskBits *	The bitmask to be applied to the subnet being created. Valid values: 1 through 32	Field Name: MaskBits Type: Integer
SubnetID *	This is the same value as the Identity. You must specify either an Identity or a SubnetID, but you cannot specify both. Whatever value you supply to one will automatically be applied to the other.	Field Name: SubnetID Type: String
NetworkSiteID	The site ID of the site to which this subnet belongs. You can retrieve site IDs for your deployment by calling the Get-CsNetworkSite cmdlet.	Field Name: NetworkSiteID Type: String
Identity *	The unique subnet ID of the subnet being created. This must be an IP address (such as 174.11.12.0), and it must be the first address in the IP address range defined by the subnet.	Field Name: Identity Type: String

Model: device/skypeforbusiness/CsNetworkSubnet