SNMP ANDing Một phương pháp được sử dụng bởi các bộ định tuyến mà nó so sánh hoặc "ands" một địa chỉ IP với subnet mask của nó để xác định địa chỉ mạng. AppleTalk Một kiến trúc mạng định tuyến được phát triển bởi Apple cung cấp dịch vụ mạng máy tính Apple Macintosh. | The Cisco Three-Layer Hierarchical Model 33 for instance hierarchy dictates that you ask your boss not your subordinate. That is the person whose role it is to grant or deny your request. Hierarchy has many of the same benefits in network design that it does in other areas of life. When used properly it makes networks more predictable. It helps us define at which levels of hierarchy we should perform certain functions. Likewise you can use tools such as access lists at certain levels in hierarchical networks and avoid them at others. Let s face it large networks can be extremely complicated with multiple protocols detailed configurations and diverse technologies. Hierarchy helps us summarize a complex collection of details into an understandable model. Then as specific configurations are needed the model dictates the appropriate manner to apply them. The Cisco hierarchical model can help you design implement and maintain a scalable reliable cost-effective hierarchical internetwork. Cisco defines three layers of hierarchy as shown in Figure each with specific functions. FIGURE The Cisco hierarchical model The following are the three layers The Core layer The Distribution layer The Access layer Copyright 2000 SYBEX Inc. Alameda CA 34 Chapter 1 Internetworking Each layer has specific responsibilities. Remember however that the three layers are logical and are not necessarily physical devices. Consider the OSI model another logical hierarchy. The seven layers describe functions but not necessarily protocols right Sometimes a protocol maps to more than one layer of the OSI model and sometimes multiple protocols communicate within a single layer. In the same way when we build physical implementations of hierarchical networks we may have many devices in a single layer or we might have a single device performing functions at two layers. The definition of the layers is logical not physical. Before you learn about these layers and their functions .
