Chapter 1 Reading Organizer

Transcription

1 Chapter 1 Reading Organizer After completion of this chapter, you should be able to: Describe convergence of data, voice and video in the context of switched networks Describe a switched network in a small to medium-sized business Explain the process of frame forwarding in a switched network Compare a collision domain to a broadcast domain 1.1 LAN Design 1. List and describe features you might find in a converged network with collaboration support. a. Call control Telephone call processing, caller ID, call transfer, hold, and conference b. Voice messaging Voic c. Mobility Receive important calls wherever you are d. Automated attendant Serve customers faster by routing calls directly to the right department or individual 2. What is the primary benefit of transitioning to a converged network? There is just one physical network to install and manage. 3. The Cisco Borderless Network is a network architecture that combines several innovations and design considerations to allow organizations to: a. connect anyone b. anywhere c. anytime d. on any device securely e. reliably f. seamlessly

2 4. List and explain borderless switched network design guideline principles. a. Hierarchical Facilitates understanding the role of each device at every tier, simplifies deployment, operation, and management, and reduces fault domains at every tier b. Modularity Allows seamless network expansion and integrated service enablement on an on-demand basis c. Resiliency Satisfies user expectations for keeping the network always on d. Flexibility Allows intelligent traffic load sharing by using all network resources 5. What are the two time-tested and proven hierarchical design frameworks for campus networks? a. The three-tier layer model b. The two-tier layer model 6. List and explain the three layers of the three-tier layered model. a. Access Layer The access layer represents the network edge, where traffic enters or exits the campus network. b. Distribution Layer The distribution layer interfaces between the access layer and the core layer to provide many important functions. c. Core Layer The core layer is the network backbone. It connects several layers of the campus network. 7. The core layer provides many important functions, these include: a. Aggregating large-scale wiring closet networks b. Aggregating Layer 2 broadcast domains and Layer 3 routing boundaries c. Providing intelligent switching, routing, and network access policy functions to access the rest of the network d. Providing high availability through redundant distribution layer switches to the end-user and equal cost paths to the core e. Providing differentiated services to various classes of service applications at the edge of network 8. What is the primary purpose of the core layer?

3 To provide fault isolation and high-speed backbone connectivity. 9. In a two-tier campus network design for an enterprise campus which layers are collapsed into a single layer? a. distribution layer b. core layer 10. Match the hierarchical switch characteristics to their term. 11. A switched LAN allows more flexibility, traffic management, and additional features, such as: a. Quality of service b. Additional security c. Support for wireless networking and connectivity d. Support for new technologies, such as IP telephony and mobility services 12. What is a fixed configuration switch? Fixed configuration switches do not support features or options beyond those that originally came with the switch. 13. Explain what a modular configuration switch is? Modular configuration switches offer more flexibility in their configuration. Modular configuration switches typically come with different sized chassis that allow for the installation of different numbers of modular line cards 14. What is a stackable configuration switch? Stackable configuration switches can be interconnected using a special cable that provides highbandwidth throughput between the switches

4 15. Match the following terms to their correct definitions. Stackable Power Reliability Scalability Port Density Price Modular Port Speed Frame Buffers Fixed Configuration Affected by the number of network devices to support Redundancy through PoE How fast the interfaces will process network data Continuous access to the network Affected by the number of interfaces, features and expandability The capacity to store frames in the cache Ability to adjust to growth of network users Switches with adjustable switching line/port cards Switches with pre-set features or options Daisy-chain switches with high-bandwidth throughput 1.2 The Switched Environment 16. The fundamental concept of switching refers to a device making a decision based on two criteria. List and explain both criteria. a. Ingress port The term ingress is used to describe where a frame enters the device on a port. b. Destination address the destination address of the message. 17. How does a switch use MAC addresses? To direct network communications through the switch to the appropriate port toward the destination. 18. As the switch learns the relationship of ports to devices where does store the information?

5 a. a MAC address table b. a content addressable memory (CAM) table 19. Where does a switch get its information from to build its MAC address table? By recording the MAC address of each device connected to each of its ports. 20. A switch populates the MAC address table based on source MAC addresses. Explain this process in excruciating detail. (More than one sentence) When a switch receives an incoming frame with a destination MAC address that is not found in the MAC address table, the switch forwards the frame out of all ports (flooding) except for the ingress port of the frame. When the destination device responds, the switch adds the source MAC address of the frame and the port where the frame was received to the MAC address table. In networks with multiple interconnected switches, the MAC address table contains multiple MAC addresses for a single port connected to the other switches. 21. Why were Ethernet bridges (an early version of a switch) added to networks? To limit the size of the collision domains 22. Explain the store-and-forward method of switching. The store-and-forward method makes a forwarding decision on a frame after it has received the entire frame and then checked the frame for errors. 23. Explain the cut-through method of switching. The cut-through method, as shown in Figure 2 begins the forwarding process after the destination MAC address of an incoming frame and the egress port has been determined. 24. Store-and-forward switching has two primary characteristics that distinguish it from cut-through. List and explain both of these. a. Error checking A switch using store-and-forward switching performs an error check on an incoming frame. After receiving the entire frame on the ingress port the switch compares the frame-checksequence (FCS) value in the last field of the datagram against its own FCS calculations. b. Automatic buffering The ingress port buffering process used by store-and-forward switches provides the flexibility to support any mix of Ethernet speeds. 25. Which switching method does Cisco primarily use? Store-and-forward

6 26. Explain why Cisco prefers this method. A store-and-forward switch drops frames that do not pass the FCS check, therefore does not forward invalid frames. By contrast, a cut-through switch may forward invalid frames because no FCS check is performed. 27. What is an advantage to cut-through switching? It has the ability of the switch to start forwarding a frame earlier than store-and-forward switching. 28. There are two primary characteristics of cut-through switching. These are: a. rapid frame forwarding b. invalid frame processing 29. Fragment free switching is a modified form of cut-through switching. Explain how this works. The switch waits for the collision window (64 bytes) to pass before forwarding the frame. This means each frame will be checked into the data field to make sure no fragmentation has occurred. 30. Explain why is fragment free a better choice than cut-through? Fragment free mode provides better error checking than cut-through, with practically no increase in latency. 31. Match the descriptions with the correct switching method.

7 32. What is a collision domain? Network segments that share the same bandwidth between devices. 33. What network devices can be used to break up collision domains? a. Router b. Switch 34. A collection of interconnected switches forms a single broadcast domain. 35. What is another name for a Layer 2 broadcast domain? MAC broadcast domain 36. Explain what happens when a switch receives a broadcast frame. It forwards the frame out each of its ports, except the ingress port where the broadcast frame was received 37. How does adding more switches effect a broadcast domain? The broadcast domain is increased 38. LAN switches have special characteristics that make them effective at alleviating network congestion. Explain. a. First, they allow the segmentation of a LAN into separate collision domains. Each port of the switch represents a separate collision domain and provides the full bandwidth to the device or devices that are connected to that port. b. Second, they provide full-duplex communication between devices. 39. List and explain some important characteristics of switches that contribute to alleviating network congestion. a. High port density Switches have high-port densities: 24- and 48-port switches are often just 1 rack unit (1.75 inches) in height and operate at speeds of 100 Mb/s, 1 Gb/s, and 10 Gb/s. Large enterprise switches may support many hundreds of ports. b. Large frame buffers The ability to store more received frames before having to start dropping them is useful, particularly when there may be congested ports to servers or other parts of the network.

8 c. Port speed Depending on the cost of a switch, it may be possible to support a mixture of speeds. Ports of 100 Mb/s, and 1 or 10 Gb/s are common (100 Gb/s is also possible). d. Fast internal switching Having fast internal forwarding capabilities allows high performance. The method that is used may be a fast internal bus or shared memory, which affects the overall performance of the switch. e. Low per-port cost Switches provide high-port density at a lower cost. For this reason, LAN switches can accommodate network designs featuring fewer users per segment, therefore, increasing the average available bandwidth per user. 40. Draw circles around each broadcast domain. a. b. c.

9 d. 40. Draw circles around each collision domain. a. b. c.

10 d.