The neutron-plugin-agent, also known as the Neutron ML2 agent or Neutron Modular Layer 2 agent, is a component of the OpenStack Neutron networking service. Neutron is responsible for providing network connectivity and networking services for virtual machines (VMs) and other instances within an OpenStack cloud environment.
The neutron-plugin-agent is specifically responsible for managing the integration between the Neutron service and the underlying network infrastructure. It acts as a bridge between the Neutron server and the network switches, routers, and other devices that make up the physical network. Its main role is to translate the logical network abstractions defined by the Neutron service into the appropriate configuration and commands for the network infrastructure.
Here are some key points about the neutron-plugin-agent:
- Modular Layer 2 (ML2) Driver: The neutron-plugin-agent is part of the ML2 plugin architecture in Neutron. The ML2 plugin provides a flexible framework for supporting multiple networking technologies and drivers. The neutron-plugin-agent serves as the ML2 driver that interacts with the underlying network devices.
- Network Abstraction: Neutron allows users to define logical networks, subnets, routers, and other network resources through its API. The neutron-plugin-agent translates these logical abstractions into the necessary configuration on the physical network devices to establish the desired network connectivity.
- Network Type Support: The neutron-plugin-agent supports various network types, including flat networks, VLANs, VXLANs, and GRE tunnels. It can configure and manage the corresponding network segments on the physical infrastructure based on the user’s network configuration.
- Security Group Enforcement: Neutron provides security groups, which are sets of IP filter rules that govern inbound and outbound traffic for instances. The neutron-plugin-agent enforces these security group rules by configuring the appropriate access control lists (ACLs) on the network devices.
- L2 Population: The neutron-plugin-agent supports the L2 population feature, which optimizes the network traffic by reducing the reliance on the Neutron server for routing traffic between VMs within the same network segment. It achieves this by programming the necessary forwarding rules on the network devices.
- Plugin-Specific Drivers: The neutron-plugin-agent can interact with different networking plugins and their respective drivers. The driver specific to the chosen networking technology is responsible for implementing the necessary operations on the network devices. For example, if the plugin uses Open vSwitch, the corresponding OVS driver is used by the neutron-plugin-agent to configure the OVS switches.
Overall, the neutron-plugin-agent plays a crucial role in enabling network connectivity and managing the integration between the Neutron service and the underlying physical network infrastructure in an OpenStack cloud environment.