Enable Networking

Configuring Networking can be a bewildering experience. The following example shows the simplest production-ready configuration that is available: the legacy networking in OpenStack Compute, with a flat network, that takes care of DHCP.

This set up uses multi-host functionality. Networking is configured to be highly available by distributing networking functionality across multiple hosts. As a result, no single network controller acts as a single point of failure. This process configures each compute node for networking.

	Note
	If you need the full software-defined networking stack, see Chapter 9, Install the Networking service.

Install the appropriate packages for compute networking on the compute node only. These packages are not required on the controller node.
So that the nova-network service can forward metadata requests on each compute node, each compute node must install the nova-api-metadata service, as follows:
```
# apt-get install nova-network nova-api-metadata
```
Note
As noted previously, you do not need to install these packages on the controller node.

Edit the nova.conf file to define the networking mode:

Edit the /etc/nova/nova.conf file and add these lines to the [DEFAULT] section:

[DEFAULT]
...

network_manager=nova.network.manager.FlatDHCPManager
firewall_driver=nova.virt.libvirt.firewall.IptablesFirewallDriver
network_size=254
allow_same_net_traffic=False
multi_host=True
send_arp_for_ha=True
share_dhcp_address=True
force_dhcp_release=True
flat_network_bridge=br100
flat_interface=eth1
public_interface=eth1

Restart the network service:
```
# service nova-network restart
```

Create a network that virtual machines can use. Do this once for the entire installation and not on each compute node. Run the nova network-create command on the controller:

# source openrc.sh

# nova network-create vmnet --fixed-range-v4=10.0.0.0/24 \
  --bridge=br100 --multi-host=T

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	Note
	As noted previously, you do not need to install these packages on the controller node.