| 1. | For each layer of the OSI model, match the forwarding criteria used by a switch: ___ Layer 1 | A. IP address | ___ Layer 2 | B. UDP/TCP port | ___ Layer 3 | C. None | ___ Layer 4 | D. MAC address |
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| Answer: | C Layer 1 | A. IP address | D Layer 2 | B. UDP/TCP port | A Layer 3 | C. None | B Layer 4 | D. MAC address |
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| 2. | What is multilayer switching (MLS)? |
| Answer: | MLS forwards traffic using information from Layer 2, Layer 3, and Layer 4all in hardware at wire speed. |
| 3. | Fill in the blanks in the following statement: In the 20/80 rule of networking, 20 percent of the traffic on a segment usually stays ______, while 80 percent travels ________________. |
| Answer: | local, travels across the network |
| 4. | What is a collision domain, and where does it exist in a switched LAN? |
| Answer: | A collision domain is a network segment where shared media access is supported. Devices on the shared media must compete for access when transmitting data. In a switched network, the collision domain is restricted to a single switch port and does not extend across the switch. |
| 5. | What is a broadcast domain, and where does it exist in a switched LAN? |
| Answer: | A broadcast domain is the extent of a network where broadcast frames propagate. Basically, a broadcast domain covers an area where Layer 2 devices are located and terminates at the boundary of a Layer 3 device. In a switched network, the broadcast domain extends to all switch ports assigned to a common VLAN. This is because a switch forwards broadcasts out all available ports in a VLAN. |
| 6. | What is a VLAN, and why is it used? |
| Answer: | A virtual LAN (VLAN) is a group of switch ports that communicate as if they were attached to a single shared-media LAN segment. VLANs can extend across buildings or backbones, as long as the VLAN is connected end to end through trunking or physical connections. A VLAN is a broadcast domain. VLANs segment networks for ease of management and better performance. |
| 7. | At what OSI layers do devices in the distribution layer usually operate? |
| Answer: | Layers 2, 3, and 4 |
| 8. | What is network segmentation? When is it necessary, and how is it done in a campus network design? |
| Answer: | Segmentation is the process of dividing a LAN into smaller, discrete collision domains. If a large percentage of collisions is observed on a LAN, segmentation is appropriate. In a campus network design, segmentation occurs at each switch port. A similar form of segmentation involves reducing the size of broadcast domains. Placing Layer 3 devices in the distribution and core layers terminates the broadcast domains at those layer boundaries. |
| 9. | Is it possible to use Layer 2 switches in the distribution layer rather than Layer 3 switches? If so, what are the limitations? |
| Answer: | It is generally best practice to use Layer 3 or multilayer switches in the distribution layer, as outlined in this chapter. However, in some environments, this might not be possible because of cost or implementation logistics. Layer 2 switches will work fine in the distribution layer but will not provide a VLAN or broadcast domain boundary in that layer. As a result, broadcasts will propagate into the core layer, using unnecessary bandwidth. |
