The Cisco EtherSwitch service modules provide Cisco modular access routers the ability to stack Cisco EtherSwitch service modules as Layer 2 switches using Cisco StackWise technology. The Cisco EtherSwitch service modules are supported by either the IP base image (formerly known as standard multilayer image (SMI)) or the IP services image (formerly known as the enhanced multilayer image (EMI)). The IP base provides Layer 2+ features, including access control lists (ACLs), quality of service (QoS), static routing, and the Routing Information Protocol (RIP). IP services provide a richer set of enterprise-class features, including Layer 2+ features and full Layer 3 routing (IP unicast routing, IP multicast routing, and fallback bridging).