Juju Charm - Neutron Gateway
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Neutron provides flexible software defined networking (SDN) for OpenStack.

This charm is designed to be used in conjunction with the rest of the OpenStack related charms in the charm store to virtualize the network that Nova Compute instances plug into.

Neutron supports a rich plugin/extension framework for propriety networking solutions and supports (in core) Nicira NVP, NEC, Cisco and others…

See the upstream Neutron documentation for more details.


In order to use Neutron with OpenStack, you will need to deploy the nova-compute and nova-cloud-controller charms with the network-manager configuration set to ‘Neutron’:

    network-manager: Neutron

This decision must be made prior to deploying OpenStack with Juju as Neutron is deployed baked into these charms from install onwards:

juju deploy nova-compute
juju deploy --config config.yaml nova-cloud-controller
juju deploy neutron-api
juju add-relation nova-compute nova-cloud-controller
juju add-relation neutron-api nova-cloud-controller

The Neutron Gateway can then be added to the deploying:

juju deploy neutron-gateway
juju add-relation neutron-gateway mysql
juju add-relation neutron-gateway rabbitmq-server
juju add-relation neutron-gateway nova-cloud-controller
juju add-relation neutron-gateway neutron-api

The gateway provides two key services; L3 network routing and DHCP services.

These are both required in a fully functional Neutron OpenStack deployment.

See upstream Neutron multi extnet

Configuration Options

Port Configuration

All network types (internal, external) are configured with bridge-mappings and data-port and the flat-network-providers configuration option of the neutron-api charm. Once deployed, you can configure the network specifics using neutron net-create.

If the device name is not consistent between hosts, you can specify the same bridge multiple times with MAC addresses instead of interface names. The charm will loop through the list and configure the first matching interface.

Basic configuration of a single external network, typically used as floating IP addresses combined with a GRE private network:

    bridge-mappings:         physnet1:br-ex
    data-port:               br-ex:eth1
    flat-network-providers:  physnet1

neutron net-create --provider:network_type flat \
    --provider:physical_network physnet1 --router:external=true \
neutron router-gateway-set provider external

Alternative configuration with two networks, where the internal private network is directly connected to the gateway with public IP addresses but a floating IP address range is also offered.

    bridge-mappings:         physnet1:br-data external:br-ex
    data-port:               br-data:eth1 br-ex:eth2
    flat-network-providers:  physnet1 external

Alternative configuration with two external networks, one for public instance addresses and one for floating IP addresses. Both networks are on the same physical network connection (but they might be on different VLANs, that is configured later using neutron net-create).

    bridge-mappings:         physnet1:br-data
    data-port:               br-data:eth1
    flat-network-providers:  physnet1

neutron net-create --provider:network_type vlan \
    --provider:segmentation_id 400 \
    --provider:physical_network physnet1 --shared external
neutron net-create --provider:network_type vlan \
    --provider:segmentation_id 401 \
    --provider:physical_network physnet1 --shared --router:external=true \
neutron router-gateway-set provider floating

This replaces the previous system of using ext-port, which always created a bridge called br-ex for external networks which was used implicitly by external router interfaces.

Instance MTU

When using Open vSwitch plugin with GRE tunnels default MTU of 1500 can cause packet fragmentation due to GRE overhead. One solution is to increase the MTU on physical hosts and network equipment. When this is not possible or practical the charm’s instance-mtu option can be used to reduce instance MTU via DHCP.

juju set neutron-gateway instance-mtu=1400

OpenStack upstream documentation recommends a MTU value of 1400: OpenStack documentation

Note that this option was added in Havana and will be ignored in older releases.