42. 数据链路层功能 ( 续 ) 数据 目标 SAP 源 SAP 数据 源地址 FCS 长度 目标地址 可变长 1 1 802.2 (SAP) MAC 子层 - 802.3 Ctrl 1 or 2 3 2 前导符 数据 目标 SAP AA 源 SAP AA 可变长 1 1 802.2 (SNAP) Ctrl 03 1 or 2 OR OUI ID 类型
43. 交换机和桥运行在链路层 1. 网络微分段 2. 交换机是 OSI 模型的第二层设备 , 在 OSI 参考模型的数据链路层(第二层)工作,交换机根据进入端口数据帧的 MAC 地址来过滤、转发或扩散该数据帧
Purpose: This chapter reviews general networking theory and introduces students to some of Cisco’s product line. Timing: This chapter takes approximately 1.5 hours to present. Note: This section has a product selection tool laboratory exercise at the end. Contents: Objectives—This section explains what the student will be able to do at the end of this chapter. Defining Network Components—This section displays where devices are placed in the network. Mapping Business Needs to a Hierarchical Model—This section describes the heirarchical model used in network design. OSI Model Overview—This section reviews the OSI model. Communicating Between Layers—This section describes encapsulation and de-encapsulation. Written Exercise 1—This section has a written exercise to test the students’ knowledge of the OSI model. Physical Layer Functions—This section describes the physical layer of the OSI Model. Data Link Layer Functions—This section describes the data link layer of the OSI Model. Network Layer Functions—This section describes the network layer of the OSI Model. Transport Layer Functions—This section describes the transport layer of the OSI Model.