A subnet in an NSX VPC represents an independent layer 2 broadcast domain. NSX VPC subnets are realized as overlay segments in the default transport zone of the project.

Prerequisites

You must be assigned any one of these roles in the NSX VPC:
  • VPC Admin
  • Network Admin

Procedure

  1. From your browser, log in to an NSX Manager at https://nsx-manager-ip-address.
  2. Select the required project from the Project drop-down menu, if not already selected.
  3. Click the VPCs tab and expand the details of the NSX VPC where you want to add a subnet.
  4. Expand the Connectivity section and click Set. If subnets are existing in the NSX VPC, click the subnet count.
    The Set Subnets dialog box opens.
  5. Click Add Subnet.
  6. Configure the subnet properties.
    Property Description

    Name

    Enter a name for the subnet.

    Access Mode

    Select any one of these access modes: Private, Public, Isolated.

    To learn more these access modes, see the Access Modes for NSX VPC Subnets section in NSX Virtual Private Clouds.

    By default, private is selected.

    IP Assignment

    By default, Automatic IP assignment is set for private and public subnets. It means that the system will assign an IPv4 CIDR for the subnet automatically. For a public subnet, the CIDR is assigned from the external IPv4 blocks of the NSX VPC. For a private subnet, the CIDR is assigned from the private IPv4 blocks of the NSX VPC.

    For isolated subnets, only Manual IP assignment mode is supported.

    In Manual IP assignment mode, you must enter a valid IPv4 CIDR for the subnet.

    Size

    This property is applicable only when you select the Automatic IP assignment mode.

    Select a size from the drop-down menu. System reserves four IP addresses for internal use, such as subnet network address, subnet gateway address, subnet broadcast address, DHCP server address.

    For example, if you select size as 32, you can attach a maximum of 28 workloads to the subnet.

    IP CIDR

    This property is applicable only when you select the Manual IP assignment mode.

    Enter the IPv4 subnet address in a CIDR format. For example, 172.16.0.1/24

    You can enter only one IPv4 CIDR. If the IPv4 CIDR that you entered is invalid or unavailable for assignment, the system throws an appropriate error message. You must enter a different IPv4 CIDR until the system accepts it.

    Description

    Optionally, enter a description for the subnet.
  7. Click Save.

Results

When a subnet is realized successfully in the NSX VPC, the Status column shows Successful.

Subnets in an NSX VPC are realized as overlay segments in the default transport zone of the project.

An Enterprise Admin or a Project Admin can view these overlay segments by doing these steps:

  1. Ensure that you are in the project view.
  2. Navigate to Networking > Segments.
  3. Click the VPC realized objects check box at the bottom of the Segments page.

    For example:


    This screen capture is described in the surrounding text.

    This screen capture shows two system-created segments orders_vpc_subnet and sales_vpc_subnet. These segments represent subnets in the sales_vpc, and are displayed in a read-only mode on the Segments page.

What to do next

You can now start attaching workload VMs to the subnet by using the vSphere Client.

The following subsections briefly explains some tasks that you can do after a subnet is realized in an NSX VPC.

Set subnet ports

On the Set Subnets dialog box, under the Subnet Ports column, click Set, and then click Add Subnet Port.

The workflow for adding ports on an NSX VPC subnet is the same as it is for adding ports on an NSX segment. To learn more, see the steps for adding segment ports in Create an NSX Segment.

View IPAM statistics of NSX VPC subnets

Expand the subnet details and click View IPAM Statistics. At the time of subnet creation, if DHCP in the NSX VPC is managed by NSX or by external DHCP servers, the IPAM Statistics page displays the DHCP IP pool range.

The system automatically allocates 100% of available IP addresses in the subnet to the DHCP pool range. The system reserves four IP addresses from the subnet for its internal use. The DHCP static IP pool is empty and hence it is not displayed on IPAM Statistics page. You cannot edit the system-managed DHCP pool configuration of the VPC subnet.

For example:


This screen capture is described in the surrounding text.

In this screen capture, the sales_vpc_subnet is a private subnet with size 16. The DHCP configuration for this subnet is automatically managed by NSX. The system reserves four IP addresses from the subnet for its internal use, by default. So, the remaining 12 IP addresses are automatically allocated to the DHCP IP pool range (193.0.1.3-193.0.1.14). The IP addresses are dynamically assigned to the workload VMs on the subnet from this DHCP pool range.

If you prefer to manually configure the DHCP pool ranges for dynamic and static IP assignments in the VPC subnet, you can add the subnet in the NSX VPC by running the following NSX API. Currently, the UI does not support manual DHCP configuration of NSX VPC subnets.

PUT https://<nsx-mgr>/policy/api/v1/orgs/default/projects/<project-id>/vpcs/<vpc-id>/subnets/<subnet-id>/

Example Request Body:

{
    "ipv4_subnet_size": 16,
    "access_mode": "Public",
    "resource_type": "VpcSubnet",
    "dhcp_config": {
        "enable_dhcp": true,
        "static_pool_config": {
            "ipv4_pool_size": 8
        }
    }
}

This example payload shows that you have created a public NSX VPC subnet of size 16. You have specified the size of the static IP pool as eight. Therefore, out of the total 12 IP addresses that are available for allocation to the workloads in the NSX VPC subnet, the remaining four IP addresses are allocated to the DHCP IP pool for a dynamic IP assignment.

When you view the IPAM Statistics page of this NSX VPC, the system displays the IP address utilization of both the DHCP IP pool and the static IP pool.

At the time of subnet creation, if DHCP in the NSX VPC is none, the IPAM Statistics page of the subnet displays only the static IP pool information.

View traffic statistics of NSX VPC subnets

Expand the subnet details and click View Subnet Statistics.

If you want to view the traffic statistics for the full NSX VPC, and not for a specific subnet in the VPC, expand the NSX VPC details, and then click View VPC Statistics.