Metro Ethernet is a service provider collection of layer 2 or layer 3 switches or routers connected through optical fiber. The topology may be a ring, hub and star or full or partial mesh.

Metro Ethernet may be used as pure Ethernet over synchronous digital hierarchy (SDH), Ethernet over multiprotocol label switching (MPLS) or Ethernet over dense wavelength division multiplexing (DWDM). Pure Ethernet deployments are less expensive but also less scalable and reliable. Thus, they are also limited to small-scale and experimental deployment. SDH-based deployments are useful when there is an established SDH infrastructure that is used by large service providers.

Metro Ethernet feasibility grew in the late 1990s due to new technological developments that allowed transparent traffic tunneling through virtual LANs as point-to-point or multipoint-to-multipoint circuits.

Metro Ethernet is widely used for small-scale deployments with less than a few hundred customers.