openstack-neutronlisted

# OpenStack Neutron -- Software-Defined Networking Neutron is OpenStack's networking service and the most complex component in the stack. It provides the network abstraction layer that connects every instance, container, and service in the cloud. Where physical networking uses cables, switches, and routers, Neutron virtualizes all of these into software constructs that operators manage through APIs. ## Architecture Neutron uses the **ML2 (Modular Layer 2) plugin** architecture, which separates the network model from the mechanism that implements it. The ML2 plugin supports multiple mechanism drivers -- the two primary backends for Kolla-Ansible deployments are: - **OVN (Open Virtual Network):** The recommended backend for new deployments. OVN provides distributed virtual routing, native DHCP, and security group implementation without requiring separate agents. It uses a northbound/southbound database architecture for state management. - **OVS (Open vSwitch):** The legacy backend that uses separate agents for L3 routing, DHCP, and metadata. Each function runs in its own network namespace. More mature but more complex operationally. **Network types supported:** flat (untagged), VLAN (802.1Q tagged), VXLAN (overlay tunnels), GRE (generic routing encapsulation). Single-node deployments typically use flat for provider networks and VXLAN for tenant networks. **The agent model (OVS backend):** Neutron runs multiple agents -- `neutron-openvswitch-agent` (L2 connectivity), `neut