Networks - Spanning Layer 2 networks across remote sites

There are several technologies that can be used to span a Layer 2 topology across geographically remote locations. These include:

Some more conventional methods for smaller scale Layer 2 spanning across remote locations include:

These technologies can be used alone, and in some cases, in combination, to provide a more feature-rich and flexible infrastructure. The use cases that typically employ such technologies include distributed datacenters, cloud services, virtual machine mobility, high availability clusters, and as a interim solution for network amalgamation resulting from mergers and acquisitions.