Create a subnet

A subnet is any logical or physical subdivision of a network consisting of a collection of IP addresses that share the same IP prefix. The prefix is represented by the leading bits in an IP address. For example, the addresses 10.3.1.3 and 10.3.1.2 are in the subnet 10.3.0.0/20 sharing the same leading bits in a /20 netmask. The netmask describes how many leading bits are fixed; thereby, determining the size or number of contiguous IP addresses in that subnet. 

In order for DHCP to be able to assign a lease, it must be bound to an interface within the subnet. In other words, you must set up a static IP address on the server that is within the subnet (IP range), and then allow the container to use that interface. DHCP will automatically bind to it as long as it’s there. For example, if a subnet is defined as 10.0.0.0/16, the interface should be 10.0.0.1 or similar.

To create a subnet via the NS1 portal:

1. From the Networks list, double-click a network (or press L or →) to view all subnets associated with that network. (This list will be empty if this is your first subnet for that network.)
   
   Note: At any point, use the breadcrumb navigation if you are not sure where you are in the network hierarchy.
   
   
   
   
2. From the Subnets page, click the + icon (or press N) to create a new subnet.
   
   
3. In the Create new subnet window, enter the prefix (using CIDR notation), a name for the subnet, and a brief description.
   
   Note: The CIDR is auto-populated based on the currently selected object. If the subnet 10.3.0.0/20 is currently selected, 10.3.0.0 will autofill this field.
   
   
4. Click Submit. The new subnet appears in the list.
   
   
5. Select the new subnet from the list to view associated metadata. You can adjust some of the metadata fields (including the type and tags) from the metadata pane.

You must change the subnet type to “assignment” (in the metadata pane) prior to adding it to a scope group.

Note: To create a subnet via API, refer to this article.