Cisco Networking Academy Program CCNA 1 and 2 Companion Guide, Revised part 14 is the Cisco approved textbook to use alongside version of the Cisco Networking Academy Program CCNA 1 and CCNA 2 web-based courses. The topics covered provide you with the necessary knowledge to begin your preparation for the CCNA certification exam (640-801, or 640-821 and 640-811) and to enter the field of network administration. | Page 99 Tuesday May 20 2003 2 53 PM Network Topologies 99 Figure 2-46 Hierarchical Topology Figure 2-47 Full-Mesh Topology In a partial-mesh topology at least one device maintains multiple connections to others without being fully meshed as shown in Figure 2-48. A partial-mesh topology still provides redundancy by having several alternative routes. If one route cannot be used the data takes another route even if it is longer. The partial-mesh topology is used for many telecommunications backbones as well as the Internet. Logical Topology A network s logical topology is how the hosts communicate across the medium. The two most common types of logical topology are broadcast and token passing. Page 100 Tuesday May 20 2003 2 53 PM 100 Chapter 2 Networking Fundamentals Figure 2-48 Partial-Mesh Topology Broadcast topology simply means that each host addresses its data to a particular NIC to a multicast address or to a broadcast address on the network medium. There is no order that the stations must follow to use the network. It is first come first serve. Ethernet also works this way as explained later in this course. The second logical topology is token passing. Token passing controls network access by passing an electronic token sequentially to each host. When a host receives the token it can send data on the network. If the host has no data to send it passes the token to the next host and the process repeats itself. Two examples of networks that use token passing are Token Ring and FDDI both of which are examples of token passing on a physical ring topology. Summary In this chapter you learned the following key points Historic reasons for the development of LANs and WANs A LAN consists of computers NICs peripheral devices networking media and network devices. A WAN consists of two or more LANs spanning two or more geographically separate areas. A MAN spans a metropolitan area such as a city or a suburban area. Page 101 Tuesday May 20 2003
