The Cisco NIM-ES2-4 is a 4-Port Layer 2 Gigabit EtherSwitch Network Interface Module (NIM) designed for Cisco 4000 Series Integrated Services Routers (ISR). It provides integrated Layer 2 switching capabilities, allowing Cisco ISR routers to support additional Gigabit Ethernet switch ports for connecting IP phones, wireless access points, workstations, video devices, and other network equipment.