Adding a network

You can add a Flat, VLAN, or Geneve network in the IBM® Cloud Infrastructure Center.

Follow the next steps to add a network:

1. On the Networks page, click Add Network.

2. On the Add Network page that you are redirected to, enter the value for the following items:

   • Enter the Name.

   • Select a network Type as Flat or VLAN or Geneve.

   • Enter the VLAN ID when the network Type is VLAN.

   • Select the Virtualization type as Open vSwitch or MacVTap for the KVM hypervisor or z/VM vSwitch for the z/VM hypervisor.

     • Open vSwitch is valid for Flat or VLAN or Geneve network type.
     • MacVTap is valid for Flat or VLAN network type. For Geneve network type, MacVTap is not supported.

   • Enter the MTU value.

   • If you add a Flat or VLAN network, there are 2 more checkboxes:

     • Shared across projects: If checked, the network is shared across all projects.
     • External Network: Specify whether the network has an external routing facility. It displays only when the Flat or VLAN network virtualization type is Open vSwitch that is to say it is a KVM network. If checked, the network is allowed to be set as a router's gateway. Editing it from checked to unchecked might fail when the network is associated with a router.

     Note, when the External network checkbox is checked, the Shared across projects checkbox needs to be checked too. Otherwise, deploying with this network by non-admin users encounters errors.

   • If you are an administrator or network administrator in the ibm-default project, select a project from Project drop down list to specify project to create the network.

3. For the KVM hypervisor, you need choose the IP address type as static or DHCP. For z/VM®, the IP address type is only allowed to be static. When you want to add a DHCP network, check that you do not have a DHCP server already running in your environment, more specifically on the subnet you want to use. The reason is that the IBM Cloud Infrastructure Center creates a DHCP server for the DHCP network, if there is a DHCP server already running, it results in messy race conditions on the network and much confusion.

   Note, DHCP is not supported for MacVTap Virtualization type.

4. Towards the end of the page, click Add Subnet, then you are redirected to the Add Subnet page. Enter the Name, Subnet mask, Gateway, and other information, as needed. Then click Add button and the subnet is added to the network. For z/VM®, it is allowed to add multiple subnets in one network. For KVM, it is allowed to add one subnet in one network, only.

5. After the subnet information is added, click Add Network at the end of the Add Network page. After a few seconds, the network is added to Networks page.

• For the z/VM hypervisor, if you create a Flat network, make sure that the VSWITCH that is configured in IBM Cloud Infrastructure Center is a VLAN Unaware Layer2 VSWITCH ; if you create a VLAN network, make sure that the VSWITCH that is configured is a VLAN Aware Layer2 VSWITCH . For more information, see Planning for z/VM networks.

• You can create only one Flat Network in IBM Cloud Infrastructure Center.

• You can create multiple VLANs. When you create VLANs, VLAN ID must be an integer in the range 1 - 4094 and can't be duplicated.

• Geneve network is only applicable to RHEL KVM hypervisors. That is to say, Geneve network is selectable when the virtualization type is Open vSwitch.

• Geneve network is not supported to be shared across projects from the IBM Cloud Infrastructure Center Web UI. Refer to Share a Geneve network with specific projects when you need to share a Geneve network with a specific project or all projects.

• When you use command-line interface to create a network, virtualization type must be added by adding --tag ovs for the KVM hypervisor or --tag zvs for the z/VM hypervisor.

• For the z/VM hypervisor, you can create multiple subnets in one network. For the KVM hypervisor, you can create one subnet in one network.

• The Primary DNS and Secondary DNS input boxes are optional. You can input DNS name servers that you plan to set for virtual machines that are deployed by using this network.

• The Starting IP address and Ending IP address contents can be automatically determined by the Subnet mask and Gateway input. You also can change them or add extra ranges. Make sure that the IP ranges are aligned with Subnet mask and Gateway input.

• The default value of the MTU (Maximum Transmission Unit) is 1500 for Flat and VLAN networks; 1442 for Geneve network. The allowed range values are from 1000 to 9000. If a value bigger than 1500(for Flat and VLAN networks) or 1442(for Geneve networks) needs to be used, then ask the IBM Cloud Infrastructure Center administrator to change the value of global_physnet_mtu option under [DEFAULT] section of /etc/neutron/neutron.conf file on the management node. Run icic-services neutron restart to make the change take effect.

• When a DHCP network is created, the IBM Cloud Infrastructure Center consumes 2 IP addresses as the DHCP ports, you can check in the IP Addresses tab from the network's detail page. Usually, the first 2 IP addresses of the IP ranges are taken.

• To deploy an RHCOS** operation system virtual machine on a KVM host, check Add RHCOS kvm network for more details.

• When adding two networks, ensure that each network is assigned a unique IP address range. If two different networks are configured with the same IP range, there is a risk that duplicate IP addresses can be assigned. To avoid IP conflicts, always assign distinct and non-overlapping IP ranges when creating multiple networks.

  The current IBM Cloud Infrastructure Center design does not enforce a restriction on using the same IP address range across different networks at the time of Add Network. However, during VM deployment, if a single network and a conflicting IP address are used, IBM Cloud Infrastructure Center will raise an IP conflict error.