1.3.3. OpenStack Networking

The OpenStack Networking service provides a scalable and API-driven system for managing the Red Hat OpenStack network and IP addresses. Because the OpenStack network is software-defined, it can easily and quickly react to changing network needs (for example, creating and assigning new IP addresses).
Among its advantages:
  • Users can create networks, control traffic, and connect servers and devices to one or more networks.
  • OpenStack offers flexible networking models, so that administrators can change the networking model to adapt to their volume and tenancy.
  • IPs can be dedicated or floating; floating IPs allow dynamic traffic rerouting.
The following networking models are currently available:
  • Flat Network Manager - The network administrator specifies a subnet, and IP addresses for VM instances are taken from the subnet and injected into the image upon launch. The Linux networking bridge is manually configured.
  • Flat DHCP Network Manager - IP addresses are taken from the DHCP server (dnsmasq). The networking bridge is still manually configured.
  • Flat VLAN Network Manager (default mode)- A VLAN and bridge are automatically created for each project. The project is assigned a range of private IPs that are only accessible from inside the VLAN. Subnets can be defined by the network administrator, and assigned dynamically as required.
OpenStack Networking is composed of:
  • quantum-server Python daemon, which manages user requests (and exposes the API)
  • L3-agent, which provides L3/NAT forwarding.
  • plugin-agent, which run on each hypervisor to perform local vswitch configuration.
  • dhcp-agent, which provides DHCP services to tenant networks.
  • MySQL database, for persistent storage.