In this chapter, we are going to learn about the concepts of metro Ethernet technology, a technology that is very popular in extending the service provider’s network to give Ethernet-like feature. Early technologies were limited to a single link known as local area networks (LANs). From a multiple access protocol in a LAN, advancement in the Ethernet technology has placed it as a ubiquitous transport technology reaching into metro and wide area networks. It has been the indisputable and the most preferable technology of choice for LAN connectivity for nearly 40 years because of its several advantages. This chapter is going to provide us more information on understanding the concepts and underlying technologies for extending the Ethernet services, i.e., from basic Ethernet to carrier-grade Ethernets. The metro Ethernet network is one such effort of establishing or extending an Ethernet LAN technology to the metropolitan area networks, through the service provider’s network. The metro Ethernet network has to replace the traditional voice-grade leased line service with legacy technologies based on time-division multiplexing and the synchronous optical networking/synchronous digital hierarchy due to the fact that these legacy technologies are inadequate for handling the high bandwidth demands of emerging data applications.