Routed Control Plane Networks

This section describes configuration for routed control plane networks. This is an advanced concept and generally applies only to larger deployments that exceed the reasonable size of a broadcast domain.

Concept

Kayobe currently supports the definition of various different networks - public, internal, tunnel, etc. These typically map to a VLAN or flat network, with an associated IP subnet. When a cloud exceeds the reasonable size of a single VLAN/subnet, or is physically distributed, this approach no longer works.

One way to resolve this is to have multiple subnets that map to a single logical network, and provide routing between them. This is a similar concept to Neutron’s routed provider networks, but for the control plane networks.

Limitations

There are currently a few limitations to using routed control plane networks. Only the following networks have been tested:

  • admin_oc

  • internal

  • tunnel

  • storage

  • storage_mgmt

Additionally, only compute nodes and storage nodes have been tested with routed control plane networks - controllers were always placed on the same set of networks during testing.

Bare metal provisioning (of the overcloud or baremetal compute) has not been tested with routed control plane networks, and would not be expected to work without taking additional steps.

Configuration

The approach to configuring Kayobe for routed control plane networks is as follows:

  • create groups in the inventory for the different sets of networks

  • place hosts in the appropriate groups

  • move vip_address and fqdn network attributes to global variables <configuration-kolla-ansible-api-addresses>

  • move global network name configuration to group variables

  • add new networks to configuration

  • add network interface group variables

Example

In this example, we initially have a number of different logical networks:

  • public_0

    • 10.0.0.0/24

    • VLAN 100

  • internal_0

    • 10.0.1.0/24

    • VLAN 101

  • tunnel_0

    • 10.0.2.0/24

    • VLAN 102

  • storage_0

    • 10.0.3.0/24

    • VLAN 103

  • storage_mgmt_0

    • 10.0.4.0/24

    • VLAN 104

Initially the following hosts are connected to these networks:

  • controllers[0:2]: public_0, internal_0, tunnel_0, storage_0

  • compute[0:127]: internal_0, tunnel_0, storage_0

  • storage[0:63]: internal_0, storage_0, storage_mgmt_0

Now consider that we wish to add 128 compute nodes and 64 storage nodes. This would exceed size of the current subnets. We could increase the subnet sizes, but there are good reasons to keep broadcast domains reasonably small.

To resolve this, we can add some more networks:

  • internal_1

    • 10.1.1.0/24

    • VLAN 111

  • tunnel_1

    • 10.1.2.0/24

    • VLAN 112

  • storage_1

    • 10.1.3.0/24

    • VLAN 113

  • storage_mgmt_1

    • 10.1.4.0/24

    • VLAN 114

The network must provide routes between the following networks:

  • internal_0 and internal_1

  • tunnel_0 and tunnel_1

  • storage_0 and storage_1

  • storage_mgmt_0 and storage_mgmt_1

Now we can connect the new hosts to these networks:

  • compute[128:255]: internal_1, tunnel_1, storage_1

  • storage[64:127]: internal_1, storage_1, storage_mgmt_1

Inventory

To model this change we could use an inventory such as the following:

inventory/hosts
localhost ansible_connection=local

[controllers]
controller[0:2]

[compute]
compute[0:255]

[storage]
storage[0:127]

[network-0]
controller[0:2]

[compute-network-0]
compute[0:127]

[storage-network-0]
storage[0:63]

[network-0:children]
compute-network-0
storage-network-0

[network-1]

[compute-network-1]
compute[128:255]

[storage-network-1]
storage[64:127]

[network-1:children]
compute-network-1
storage-network-1

Kolla API addresses

Remove all variables defining vip_address or fqdn network attributes from networks.yml, and move the configuration to the API address variables <configuration-kolla-ansible-api-addresses> in kolla.yml.

Network names

To move global network name configuration to group variables, the following variables should be commented out in networks.yml:

networks.yml
#admin_oc_net_name:
#internal_net_name:
#tunnel_net_name:
#storage_net_name:
#storage_mgmt_net_name:

Create group variable files in inventory/group_vars/network-0 and inventory/group_vars/network-1:

inventory/group_vars/network-0
admin_oc_net_name: internal_0
internal_net_name: internal_0
tunnel_net_name: tunnel_0
storage_net_name: storage_0
storage_mgmt_net_name: storage_mgmt_0
inventory/group_vars/network-1
admin_oc_net_name: internal_1
internal_net_name: internal_1
tunnel_net_name: tunnel_1
storage_net_name: storage_1
storage_mgmt_net_name: storage_mgmt_1

Networks

Now, ensure both sets of networks are defined in networks.yml. Static routes are added between the pairs of networks here, although these will depend on your routing configuration. Other network attributes may be necessary, we are including cidr, vlan and routes only here for brevity:

networks.yml
public_0_cidr: 10.0.0.0/24
public_0_vlan: 100

internal_0_cidr: 10.0.1.0/24
internal_0_vlan: 101
internal_0_routes:
  - cidr: "{{ internal_1_cidr }}"
    gateway: 10.0.1.1

internal_1_cidr: 10.1.1.0/24
internal_1_vlan: 111
internal_1_routes:
  - cidr: "{{ internal_0_cidr }}"
    gateway: 10.1.1.1

tunnel_0_cidr: 10.0.2.0/24
tunnel_0_vlan: 102
tunnel_0_routes:
  - cidr: "{{ tunnel_1_cidr }}"
    gateway: 10.0.2.1

tunnel_1_cidr: 10.1.2.0/24
tunnel_1_vlan: 112
tunnel_1_routes:
  - cidr: "{{ tunnel_0_cidr }}"
    gateway: 10.1.2.1

storage_0_cidr: 10.0.3.0/24
storage_0_vlan: 103
storage_0_routes:
  - cidr: "{{ storage_1_cidr }}"
    gateway: 10.0.3.1

storage_1_cidr: 10.1.3.0/24
storage_1_vlan: 113
storage_1_routes:
  - cidr: "{{ storage_0_cidr }}"
    gateway: 10.1.3.1

storage_mgmt_0_cidr: 10.0.4.0/24
storage_mgmt_0_vlan: 104
storage_mgmt_0_routes:
  - cidr: "{{ storage_mgmt_1_cidr }}"
    gateway: 10.0.4.1

storage_mgmt_1_cidr: 10.1.4.0/24
storage_mgmt_1_vlan: 114
storage_mgmt_1_routes:
  - cidr: "{{ storage_mgmt_0_cidr }}"
    gateway: 10.1.4.1

Network interfaces

Since there are now differently named networks, the network interface variables are named differently. This means that we must provide a group variables file for each set of networks and each type of host. For example:

inventory/group_vars/compute-network-0/network-interfaces
internal_0_interface: eth0.101
tunnel_0_interface: eth0.102
storage_0_interface: eth0.103
inventory/group_vars/compute-network-1/network-interfaces
internal_1_interface: eth0.111
tunnel_1_interface: eth0.112
storage_1_interface: eth0.113
inventory/group_vars/storage-network-0/network-interfaces
internal_0_interface: eth0.101
storage_0_interface: eth0.103
storage_mgmt_0_interface: eth0.104
inventory/group_vars/storage-network-1/network-interfaces
internal_1_interface: eth0.111
storage_1_interface: eth0.113
storage_mgmt_1_interface: eth0.114

The normal interface configuration group variables files inventory/group_vars/compute/network-interfaces and inventory/group_vars/storage/network-interfaces should be removed.

Group variables for controller network interfaces may be placed in inventory/group_vars/controllers/network-interfaces as normal.

Alternative approach

There is an alternative approach which has not been tested, but may be of interest. Rather than having differently named networks (e.g. internal_0 and internal_1), it should be possible to use the same name everywhere (e.g. internal), but define the network attributes in group variables. This approach may be a little less verbose, and allows the same group variables file to set the network interfaces as normal (e.g. via internal_interface).