Configuring a private network subnet

Configure a private network subnet by using UI

To create a new subnet, complete the following steps:

You cannot assign the subnet that is already assigned to another virtual machine. However, when you edit the configuration of a virtual machine, you can assign the same subnet multiple times.

1. Log in to the IBM Cloud catalog with your IBM credentials.

2. In the search box, type Power Virtual Server and click the Power Virtual Server tile.

3. In the navigation panel, click Workspaces. The workspaces page with a list of existing workspaces is displayed.

4. Click your workspace from the list to open the virtual server instance page.

5. Click Subnets in the left navigation panel, then click Create subnet. The new subnet panel is displayed.

6. Enter a name, CIDR value (for example, '192.168.100.14/24'), gateway number (for example, '192.168.100.15'), and the IP range values for the subnet.

7. Enter the DNS server value.

   A DNS server value of 9.9.9.9 might not be reachable if you don't have a public IP. This issue can cause the LPAR to hang during the startup operation. You can use the default DNS server value of 127.0.0.1 to avoid this issue. You can add up to 20 DNS server IP addresses separated by commas.

8. Set Advertise to one of the following options:

   • Enabled: The static route is advertised to external connections. Advertise is set to Enabled by default.
   • Disabled: The static route is not advertised to external connections.

9. Set Subnet ARP Broadcast to one of the following options:

   • Enabled: Distributes the Address Resolution Protocol (ARP) traffic in the Power Virtual Server network fabric.

   • Disabled: Does not distribute the ARP traffic in the Power Virtual Server network fabric. Subnet ARP Broadcast is set to Disabled by default.

   For more information about subnet ARP broadcast, see Configuring the ARP broadcast in Power Virtual Server subnets.

10. Set DHCP to to one of the following options:

    • Enabled: Network interfaces that are configured to use Dynamic Host Configuration Protocol (DHCP) receive their IPv4 configurations automatically. DHCP is set to Enabled by default.

    • Disabled: Network interfaces that are configured to use DHCP do not receive their IPv4 configurations automatically.

    The DHCP service is available only in IBM Power Virtual Server in Client location. For more information about DHCP, see DHCP network inside the pod.

11. You can also attach a primary and redundant cloud connection to the subnet to set up high availability in an IBM data center. For more information about high availability, see Setting up high availability over cloud connections.

12. Click Create subnet.

Updating an existing subnet

Complete the following steps to update an existing subnet:

1. Click Subnets in the left navigation panel.

2. Click the subnet that you want to update from the displayed list.

3. Click Edit details to update the subnet.

You can attach or detach cloud connections to each of the subnets in the Attached cloud connections section in IBM data center.

Configure a private network subnet by using CLI

You can also create and configure a private network subnet by using the IBM command-line interface (CLI). Use the following command to create a private network subnet:

ibmcloud pi network-create-private NETWORK_NAME --cidr-block CIDR --ip-range "startIP-endIP[,startIP-endIP]" [--dns-servers "DNS1 DNS2"] [--gateway GATEWAY] [--json]

Reserving IP addresses

Use the reserved IP addresses to block Power Virtual Server from assigning a specific IP address to a virtual server instance.

You can complete the following tasks:

• Add IP address
• See the list of reserved IP addresses
• Delete the reserved IP address

An IP address that is present in the reserved list is not auto assigned to a virtual server instance.

Networking considerations for IBM data center

You can establish a private network communication between the two Power Virtual Server instances with any one of the following approaches:

1. Use a PER-enabled workspace. See, Getting started with PER.
2. Create and attach the subnet to a cloud connection and Transit Gateway.

Using CIDR notation

You can use CIDR notations if public subnets are enabled and are in use. You can specify CIDR notation for a public subnet with either an RFC 1918 IP address space (10.0.0.0/8, 172.16.0.0/12, or 192.168.0.0/16) or an IP address space registered with the Internet Assigned Numbers Authority (IANA). You must plan carefully when you use a non-RFC 1918 IP address space. If a subnet contains non-RFC 1918 IP addresses, a virtual server instance (VSI) in that subnet might not reach certain IP addresses when public networks are also attached to the VSI.

The Power Virtual Server assigns internal IP addresses from the 192.168.0.0/16 CIDR block to your account to enable connectivity to public networks. The IP addresses from the 192.168.0.0/16 block that are assigned to your account for public network use cannot be used for private networks.

The number after the slash represents the bit length of the subnet mask. As a result, the smaller the number after the slash, the more IP addresses you are allocating. The following table lists the number of available addresses in a subnet (based on its specified CIDR block size):