A LAN switch's ultimate role is to forward Ethernet frames. To achieve that goal, switches make decisions based on the source and destination MAC addresses in the Ethernet frames. When a switch receives a frame, it follows a set of rules and ultimately makes a decision out of which port or multiple ports to towards the frame. The switch logic can be summarized in a few steps: Let's start with the process of receiving frames and learning MAC addresses. Switches build their MAC address tables by examining the source MAC address of incoming Ethernet frames. When a frame is received on a switch port and the source MAC address is not known, the switch creates a new entry in the MAC table. It is important to mention that the term switchport and switch interface are used interchangeably. Also, switch's MAC address table is also called switching table and CAM table (Content-Addressable Memory Table). Shown in figure 1 is a single-switch topology. The switch hasn't yet created any entries in its MAC address table. The process starts when Client 1 sends an Ethernet frame to Client 4. Let's look closely at each steps the switch takes: The switch operations can be summarized in Figure 3. 1. Which term is used to describe the process of placing one message format into another format so that the message can be delivered across the appropriate medium? flow control encapsulation encoding multicasting access method 2. Refer to the graphic. What does the router do after it determines that a data packet from Network 1 should be forwarded to Network 2? It sends the data packet as it was received. It reassembles the frame with different MAC addresses than the original frame. It reassembles the data packet with different IP addresses than the original data packet. It reassembles both the packet and the frame with different destination IP and MAC addresses. 3. Which two statements concerning networking standards are true? (Choose two.) adds complexity to networks encourages vendors to create proprietary protocols provides consistent interconnections across networks ensures that communications work best in a single-vendor environment simplifies new product development 4. What does the 100 mean when referencing the 100BASE-T Ethernet standard? type of cable used type of data transmission speed of transmission type of connector required maximum length of cable allowed 5. Which address does an NIC use when deciding whether to accept a frame? source IP address source MAC address destination IP address destination MAC address source Ethernet address 6. Which type of address is used in an Ethernet frame header? logical addresses only IP addresses only MAC addresses only broadcast addresses only 7. What is the function of the FCS field in an Ethernet frame? detects transmission errors provides timing for transmission contains the start of frame delimiter indicates which protocol will receive the frame 8. What is the purpose of logical addresses in an IP network? They identify a specific NIC on a host device. They are used to determine which host device accepts the frame. They provide vendor-specific information about the host. They are used to determine the network that the host is located on. They are used by switches to make forwarding decisions. 9. Which device accepts a message on one port and always forwards the message to all other ports? modem switch router hub 10. Which two networking devices are used to connect hosts to the access layer? (Choose two.) router hub switch server computer 11. Host A needs to learn the MAC address of Host B, which is on the same LAN segment. A message has been sent to all the hosts on the segment asking for the MAC address of Host B. Host B responds with its MAC address and all other hosts disregard the request. What protocol was used in this scenario? ARP DHCP DNS WINS 12. A switch receives a frame with a destination MAC address that is currently not in the MAC table. What action does the switch perform? It drops the frame. It sends out an ARP request looking for the MAC address. It floods the frame out of all active ports, except the origination port. It returns the frame to the sender. 13. What device is typically used as the default gateway for a computer? a server hosted by the ISP the router interface closest to the computer a server managed by a central IT department the switch interface that connects to the computer 14. Refer to the graphic. Five PCs are connected through a hub. If host H1 wants to reply to a message from host H2, which statement is true? H1 sends a unicast message to H2, but the hub forwards it to all devices. H1 sends a unicast message to H2, and the hub forwards it directly to H2. H1 sends a broadcast message to H2, and the hub forwards it to all devices. H1 sends a multicast message to H2, and the hub forwards it directly to H2. 15. Which table does a router use to make decisions about the interface through which a data packet is to be sent? ARP table routing table network table forwarding table 16. I f the default gateway is configured incorrectly on the host, what is the impact on communications? The host is unable to communicate on the local network. The host can communicate with other hosts on the local network, but is unable to communicate with hosts on remote networks. The host can communicate with other hosts on remote networks, but is unable to communicate with hosts on the local network. There is no impact on communications. 17. What is a benefit of having a router within the distribution layer? prevents collisions on a local network keeps broadcasts contained within a local network controls which hosts have access to the network controls host-to-host traffic within a single local network 18. What type of route allows a router to forward packets even though its routing table contains no specific route to the destination network? dynamic route default route destination route generic route 19. Which two items are included in a network logical map? (Choose two.) naming scheme IP addressing scheme length of cable runs physical location of networking devices specific layout of interconnections between networking devices and hosts 20. An integrated router can normally perform the functions of which two other network devices? (Choose two.) NIC switch e-mail server application server wireless access point 21. What is a reason for disabling simple file sharing? It enables the user to map a remote resource with a local drive. It enables the user to share all files with all users and groups. It enables the user to share printers. It enables the user to set more specific security access levels. |
When a switch receives an Ethernet frame what does it do if the destination MAC address is a broadcast?
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