Summary

Chapter 8: Fundamental Networks 23lost or corrupted. Address information is added to the beginning and end of packets beforethey are transmitted. The packet, along with the address information, is called a frame.LANs are often divided into sections called segments, similar to how a company is dividedinto departments. The boundaries of segments can be defined using a bridge. A bridge is adevice used to filter network traffic between LAN segments. Bridges keep a record of allthe devices on each segment to which the bridge is connected. When the bridge receives aframe, it examines the destination address to determine if the frame is to be sent to a differentsegment, or dropped. The bridge also helps improve the flow of data by keeping framesconfined to only the segment to which the frame belongs.Switches, shown in Figure 8-12, are sometimes called multiport bridges. A typical bridgemay have just two ports, linking two segments of the same network. A switch has severalports, depending on how many network segments are to be linked. A switch is a moresophisticated device than a bridge. A switch maintains a table of the MAC addresses forcomputers that are connected to each port. When a frame arrives at a port, the switch comparesthe address information in the frame to its MAC address table. The switch then determineswhich port to use to forward the frame.Figure 8-12SwitchRoutersWhereas a switch connects segments of a network, routers, shown in Figure 8-13, aredevices that connect entire networks to each other. Switches use MAC addresses to forwarda frame within a single network. Routers use IP addresses to forward frames to other networks.A router can be a computer with special network software installed, or it can be adevice built by network equipment manufacturers. Routers contain tables of IP addressesalong with optimal destination routes to other networks.