The 4-Port Gigabit Ethernet ISE line card provides Cisco 12000 Series Routers with four optical Gigabit Ethernet interfaces on a single line card, using field replaceable SFP modules. The line card provides high-speed connections to other network devices, such as another Cisco 12000 Series Router, other routers, or layer-2 and layer-3 switches that support Gigabit Ethernet interfaces. The 4-Port Gigabit Ethernet line card throughput is limited to 4 million packets per second (4 Mpps) at 64 bytes, so all four ports cannot run at line rate.