ccna questions and answers for interview

ccna questions and answers for interview.After gaining a more in-depth understanding of copper and fiber optic cables, take a look at how the various types of Ethernet use them. The next few subsections discuss the various Ethernet implementations from a cabling and standards perspective.1. Characteristics of the Ethernet Physical LayerMany physical layer standards define the physical characteristics of Ethernet implementations, the most common of which is IEEE 802.3 10Mbit/So Table 3.12 lists some of the 10Mbit/s standards. The most common copper cable used in Ethernet is UTP.Exam Essentials To take the CCNA exam, keep the information listed in Table 3.12 in mind.Ethernet supports bus topologies-physical bus topologies and logical bus topologies. In a bus topology, all devices are connected to the same cable and all see each frame. For example, 10Base5 uses a thick coaxial cable; the NIC is connected to this cable through a plug-in connector. In 10Base2, a number of cables and BNC connectors (commonly known as T-taps) are used to connect devices together: one end of the T-tap is connected to the NIC, and the other two ends are connected to the two Ethernet cables used as the bus. Both ends of the cable that acts as a bus must be terminated. In lOBaseT, all devices are connected to a hub, which provides the logical bus topology. All these 10 Mbit/s Ethernet solutions support only half-duplex: they can send or receive, but not both at the same time. Duplex mode will be discussed in more detail in Chapter 4.Table 3.12 Features of 10 Mbit/s Ethernet10Base2 and 10Base5 Ethernet have been discarded for years because the cables they use make it difficult to troubleshoot the network. Many lOBaseT networks have been replaced by higher speed Ethernet solutions, such as Fast Ethernet and Gigabit Ethernet. Ethernet and Fast Ethernet use the same frame type and support the same CSMA/CD; however, there are two main differences between them: Fast Ethernet supports speeds of 100 Mbit/s and the physical layer is implemented differently. Table 3.13 illustrates the various Fast Ethernet implementations. Fast Ethernet supports both half-duplex and full-duplex connections; with a full-duplex connection, devices can send and receive data simultaneously, but the connection is required to be point-to-point and a hub cannot be used.As a practical matter, note that 10Base5 and 10Base2 are rarely used today; even lOBaseT has been replaced by lOOBaseTX and lOOOBaseT. For example, many laptops are pre-installed with lOOOBaseT (Gigabit Ethernet) NICoTable 3.13 Characteristics of lOOMbit/s Ethernet Ethernet Type Maximum Distance Cable Type Interface Type Physical Topology Logical TopologylOOBaseTX 100 m Category 5, 5E, 6, and 6A UTP RJ-45 Star (hub) Bus