This configuration guide describes the use and configuration of the ADRAN Operating System (AOS) Carrier Ethernet terminal loopback feature. This feature can be used to test and verify network quality and traffic management services configured for end user traffic that typically ingresses the Metro Ethernet Network (MEN) from the User Network Interface (UNI) of a remote AOS device at the customer side of the MEN. Included in this guide are an overview of the terminal loopback feature, the steps necessary to configure a terminal loopback test, and options for troubleshooting loopback test configurations.