Network requirements

Network requirementsΒΆ

Your OpenStack environment must have an efficient, scalable, and manageable network infrastructure that addresses your immediate business needs and future growth. All nodes must communicate with each other through allocated networks. Network configuration of your Fuel Slave nodes depends significantly on the network topology that you select.

Fuel deploys standard network topologies supported by Neutron, as well as extended Neutron’s networking functionality using such plugins as ML2 and so on. Neutron is a flexible network manager that enables you to create complex network configurations. Neutron provides both level 2 and 3 network virtualization, as well as IP address management (IPAM). In addition, Neutron has multiple open-source and enterprise-class plugins that enable interoperability with such networking technologies as virtual switches and software defined networking (SDN).


Since the introduction of Neutron, nova-network development efforts have been gradually reduced and may be deprecated in the future OpenStack releases. Neutron is recommended in all new deployments.

Fuel can deploy the following Neutron network topologies:

Neutron with VLAN segmentation

Similar to nova-network VLAN Manager, in Neutron’s VLAN segmentation topology a VLAN is assigned to each tenant. IP subnets and ranges in different tenants can overlap. This is the default networking option in Fuel. The disadvantage of this option is that you must configure your networking equipment, as well as provide the total number of tenants, before configuring the network.

If you select Neutron with VLAN segmentation, you must have at least 3 network interfaces (NICs).

Neutron with VLAN segmentation examples:

  3 NICs 4 NICs
eth0 Untagged port for Administrative network Port for Administrative network
eth1 (br-eth1)

Port for the following networks:

  • Public/Floating
  • Management
  • Storage

Port for the following networks:

  • Public/Floating
  • Management
eth2 (br-eth2) Port for Private network. The number of VLANs depends on the number of tenant networks with a continuous range. Port for Private network with defined VLAN ID range
eth3 (br-eth3) N/A Port for Storage network
Neutron with tunneling segmentation

You can choose between VXLAN and GRE segmentation, with VXLAN being a default and preferred option. In both VXLAN and GRE segmentations, tenant traffic is isolated by encapsulation the traffic in tunnels. Both VXLAN and GRE segmentation is more flexible in terms of the number of tenants (supports up to 65534 tenants). Network hardware configuration is significantly simpler compared to the VLAN segmentation and does not need to be synchronized with your L2 switch configuration. Both VXLAN and GRE support subnet overlapping in different tenants. However, the disadvantage of using GRE segmentation is that GRE encapsulation decreases the network speed between the instances, as well as increases the CPU usage on the compute and controller nodes.


To use VXLAN segmentation, your network hardware must support VXLAN segmentation.

You can configure GRE segmentation using CLI. For more information, see: Fuel CLI Reference.

Neutron with GRE segmentation examples:

  2 NICs 3 NICs 4 NICs
eth0 Untagged port for Administrative network Untagged port for Administrative network Untagged port for Administrative network
eth1 (br-eth1)

Port for the following networks:

  • Public/Floating
  • Management
  • Storage

Port for the following networks:

  • Public/Floating
  • Management
Port for Management network
eth2 (br-eth2) N/A Port for Storage network Port for Public/ Floating network
eth3 (br-eth3) N/A N/A Port for Storage network

Routing recommendations for Neutron networking topologies:

  • Public network: use the default routing through the router.
  • Management network: use management network to access your management infrastructure (L3 connectivity, if necessary).
  • Administrative network or only the Fuel Master node: must have the Internet access through a dedicated NIC.
  • Storage and Private networks (VLANs): isolate from other networks.

Fuel creates the default node network group that includes the Public, Storage, Management, and Baremetal networks if you installed the OpenStack Bare Metal service.

The Private network appears in the Network Settings tab if the environment networking segmentation type is tunneling segmentation. It does not appear in the Network Settings tab in case of VLAN segmentation as it has no L3 settings.

The Private network will (always) appear in the Node Interfaces Configuration tab, regardless of the segmentation type. The Private network will always be accessible through API as well.

The requirements for Public, Storage, and Management networks are:

  • For Public network
    • Floating IP range must fit into Public network CIDR of any of the node network groups in the environment and share that CIDR with Public IP ranges of that network.
    • Each deployed Controller node requires one IP address from the Public IP range.
    • If you set Assign public network to all nodes option in the Settings tab, then each deployed node requires one IP.
    • Virtual IPs and the default gateway require three additional IP addresses for the environment: two IP addresses for Virtual IPs and one IP address for the default gateway.
    • If the Neutron DVR feature is enabled, the DVR requires one additional IP address for each Compute node in case you plan to use Floating IPs in the deployment.
    • If you install plugins, refer to the plugin guides for Public IP requirements.
  • For Storage and Management networks
    • These are internal networks and, hence, the address range should be private, not globally routable.

Neutron L2 and L3 requirements are:

  • Each project’s network requires one unique VLAN ID (using VLAN segmentation) or unique segmentation ID (using GRE or VxLAN)
  • Admin project network is isolated from both private and public networks for security reasons.
  • For floating network each defined project, including the Admin project, requires one IP address from the floating IP address range. This IP address goes to the virtual interface of the project’s virtual router.
  • Direct connection to the external network requires one IP address from the floating IP range for each VM.
  • The floating IP address range should not intersect with the Public network address ranges.
  • Specify addresses for the guest OS DNS servers if you do not want to use the default DNS servers.