Cisco Gigabit Ethernet Network Module Overview as below:The Cisco Gigabit Ethernet Network Module brings Gigabit Ethernet to the Cisco 2691, Cisco 3660, Cisco 3725, Cisco 3745, Cisco 3825 and Cisco 3845.The single-port Cisco Gigabit Ethernet Network Module (part number NM-1GE) provides Gigabit Ethernet optical and copper connectivity for access routers. The module is supported by the Cisco 2691, Cisco 3660, Cisco 3725, Cisco 3745, Cisco 3825, and Cisco 3845 series routers. This network module has one gigabit interface converter (GBIC) slot to carry any standard copper or optical Cisco GBIC (see Table 1 for details). The flexibility to use different GBICs allows for making a choice depending on various factors, such as distance, cost, existing infrastructure, future expansion plans, and requirements.The Cisco Gigabit Ethernet Network Module enables branch offices to cost-effectively utilize high-speed uplinks in a variety of environments (refer to Figure 1). The enhanced performance allows customers to enable new applications and services as well as providing greater capacity for existing inter-VLAN routing and bridging capabilities. Additionally, branch offices will now have the opportunity to connect to metropolitan-area networks (MANs). Cisco IOS ® Software provides enhanced capabilities such as quality of service (QoS), network-based application recognition (NBAR), IP Security (IPSec), and Layer 3 virtual private networks (VPNs).GIGABIT ETHERNET APPLICATIONS Gigabit Ethernet in the Branch OfficeIn a branch office, the Cisco Gigabit Ethernet Network Module can provide a high-speed uplink. Figure 2 shows the module being used to bridge non-routable protocols while simultaneously providing Layer 3 connectivity. The module is also useful in situations that require inter-VLAN routing with an ISL or IEEE 802.1q trunk, and in any LAN requiring fiber connectivity.Minimum Memory RequirementsRefer to the IOS Upgrade Planner or the Cisco IOS release notes for information regarding memory requirements.