1.
A hub is connected to a switch port. Two PC's, PC1 and PC2 are connected to the hub. All the links are on ethernet communication. PC1 pings PC2. How many mac-address is learned on the switch port?
Correct Answer
B. 2
Explanation
When PC1 pings PC2, the hub will broadcast the ping message to all devices connected to it, including the switch. The switch will then learn the MAC addresses of both PC1 and PC2 because it sees the communication from both devices. Therefore, the switch port will have two MAC addresses learned.
2.
A PC that is connected to a switch port 1 is disconnected and connected to port 2. Which of the following is true w.r.t the above action?
Correct Answer
C. Mac-address of PC will be removed from the mac-address table on disconnect from port 1
Explanation
When a PC is disconnected from a switch port and connected to another port, the switch will update its mac-address table. The mac-address of the PC that was learned on port 1 will be removed from the mac-address table. This is because the switch keeps track of the mac-addresses associated with each port, and when a device is disconnected, it removes that mac-address from the table.
3.
A hub is connected to a switch port 1. A PC is connected to a hub. The PC on the hub communicates with servers residing on the switch. The PC is disconnected from the hub. Which of the following statements are true?
Correct Answer
A. The mac-address table w.r.t to port 1 of the switch will not be modified. Mac-address will be retained
Explanation
When the PC is disconnected from the hub, the switch will not modify the mac-address table for port 1. The mac-address of the PC will still be retained in the table, even though the PC is no longer connected. This is because the switch will not actively remove entries from the mac-address table unless it receives a signal that the device has been disconnected. Therefore, the statement is true.
4.
What would happen if the source and destination mac-address in an ethernet frame received on a switch port are the same?
Correct Answer
B. The frame will be filtered and discarded.
Explanation
If the source and destination MAC addresses in an Ethernet frame received on a switch port are the same, it means that the frame is a looped frame. In order to prevent network loops, switches have a mechanism called Spanning Tree Protocol (STP) that detects and disables redundant paths in the network. When a looped frame is detected, the switch will discard the frame to prevent the creation of a network loop. Therefore, the correct answer is that the frame will be filtered and discarded.
5.
Which of the following fields in an Ethernet frame is not usually checked by a layer 2 switch unless destined for itself?
Correct Answer
A. Data
Explanation
A layer 2 switch typically checks the destination MAC address in an Ethernet frame to determine where to forward the frame. However, it does not usually check the data field of the frame unless it is destined for itself. The data field contains the actual payload of the frame, such as the information being transmitted. Since the switch is primarily concerned with forwarding the frame based on the destination MAC address, it does not need to inspect the data field unless it needs to process the frame locally.
6.
A 24 port switch receives a frame with destination mac-address unknown. To how many ports will the frame be flooded?
Correct Answer
A. 23
Explanation
When a switch receives a frame with an unknown destination MAC address, it floods the frame to all ports except the one it was received on. Since the switch has 24 ports, the frame will be flooded to 23 ports, excluding the port it was received on. Therefore, the correct answer is 23.
7.
In an 802.1q encapsulated ethernet frame, which field contains the value of the upper layer protocol?
Correct Answer
A. Type field in the ethernet frame.
Explanation
In an 802.1q encapsulated ethernet frame, the field that contains the value of the upper layer protocol is the Type field in the ethernet frame. The Type field specifies the protocol being used in the data payload of the ethernet frame, allowing the receiving device to correctly interpret and process the data.
8.
A switch port operating in full-duplex mode is connected to a PC operating in half-duplex. What would be the effective duplex settings for communication?
Correct Answer
B. Half Duplex
Explanation
When a switch port is operating in full-duplex mode and is connected to a PC operating in half-duplex mode, the effective duplex settings for communication would be half duplex. This is because the communication will be limited to the capabilities of the device with the lower duplex setting, in this case, the PC. The switch will adjust its settings to match the PC's half-duplex mode, allowing for successful communication.
9.
Which form of switching can be used if the CRC value of the frame is to be calculated only by the destination?
Correct Answer
A. Cut through
Explanation
Cut through switching is a form of switching where the switch starts forwarding the frame as soon as it receives the destination address, without waiting for the entire frame to be received. In this case, the CRC value of the frame is calculated only by the destination. This means that the switch does not perform any CRC check on the frame before forwarding it. Therefore, the correct answer is Cut through.
10.
In a LAN medium which uses the Canonical format which bit will be sent last for the mac-address 00-1b-78-ab-9f-99.
Correct Answer
A. The most significant bit of the first octet (00)
Explanation
The most significant bit of the first octet (00) will be sent last for the mac-address 00-1b-78-ab-9f-99. In the Canonical format, the most significant bit is sent first, followed by the least significant bits. Therefore, in this case, the most significant bit of the first octet (00) will be sent last.
11.
Two switches sw1 and sw2 are connected using two links ( port 5 and port 6 on sw1 is connected to port 5 and port 6 on sw2 respectively). If a PC on sw1 generates a broadcast frame, how many copies of the frame would be received back by sw1 on ports 5 and 6?
Correct Answer
C. 2
Explanation
When a PC on sw1 generates a broadcast frame, it is sent out to all ports on sw1, including ports 5 and 6. Since sw2 is connected to sw1 through these ports, the broadcast frame will be received by sw2 on its corresponding ports 5 and 6. However, sw1 will not receive a copy of the broadcast frame on its own ports 5 and 6 because it originated from sw1 itself. Therefore, the correct answer is 2 copies of the frame would be received back by sw1 on ports 5 and 6.
12.
What would be the value of TYPE in an ethernet frame communicating in a TCP/IP environment in which the data is HTTP traffic?
Correct Answer
A. IP
Explanation
In an Ethernet frame communicating in a TCP/IP environment with HTTP traffic, the value of TYPE would be IP. This is because IP (Internet Protocol) is responsible for routing and addressing packets of data across the internet. TCP (Transmission Control Protocol) is a protocol that operates on top of IP and ensures reliable delivery of data. HTTP (Hypertext Transfer Protocol) is an application layer protocol that uses TCP/IP to transmit web page data. Therefore, the TYPE value in this scenario would be IP, as it represents the underlying protocol used for communication.
13.
PC1 communicates with another PC2 on the same segment of a switch. What is the destination mac-address in the frame if the mac-address of PC1 is 00-1b-78-ab-9f-90?
Correct Answer
A. The mac-address of PC2
Explanation
The destination MAC address in the frame would be the MAC address of PC2 because PC1 is communicating directly with PC2 on the same segment of a switch. The destination MAC address in the frame specifies the intended recipient of the frame, in this case, PC2.
14.
The mac-age time configured on the port of a switch is 5 minutes. A hub is connected to the port. PC1 and PC2 are connected to the hub. The mac-address of PC2 is added to the mac-address-table of the switch just before 2 minutes. Assuming no traffic has been triggered, after 2 minutes from start on both the PCs, What info would be displayed in the mac-address-table related to the port on the switch after 5 minutes?
Correct Answer
A. Mac-address of PC2
Explanation
After 5 minutes, the mac-address-table on the switch will still display only the mac-address of PC2. This is because the mac-age time configured on the port is 5 minutes, which means that any mac-address that has not been refreshed within 5 minutes will be removed from the table. Since no traffic has been triggered, the mac-address of PC2 will remain in the table as it was added just before 2 minutes and has not yet reached the 5-minute mark. The mac-addresses of PC1 and the hub port will not be displayed in the table.
15.
If reliability is required at Layer 2, what should be implemented in the design?
Correct Answer
B. LLC - Type 2
Explanation
LLC (Logical Link Control) - Type 2 should be implemented in the design if reliability is required at Layer 2. LLC - Type 2 provides error control and flow control mechanisms to ensure reliable data transmission between two nodes in a network. It handles error detection, retransmission of lost or corrupted frames, and manages the flow of data to prevent congestion. Therefore, implementing LLC - Type 2 at Layer 2 would ensure the required reliability in the network.
16.
Which of the following offers a connectionless acknowledged service?
Correct Answer
C. LLC Type 3
Explanation
LLC Type 3 offers a connectionless acknowledged service. Connectionless means that there is no established connection between the sender and receiver before data transmission. Acknowledged service means that the receiver acknowledges the successful receipt of data, ensuring reliable delivery. Therefore, LLC Type 3 provides a reliable and acknowledged data transmission service without the need for a pre-established connection.
17.
A PC is connected to a 5 port ethernet hub operating at 100 Mbps. Other ports of the hub are free and not connected to any other devices. At what duplex setting can the hub operate?
Correct Answer
A. Half duplex only
Explanation
The correct answer is half duplex only. This is because a hub is a shared medium where data is sent to all connected devices. In half duplex mode, only one device can transmit data at a time, while the others must wait. Since the other ports of the hub are free and not connected to any other devices, there is no need for full duplex operation where simultaneous bi-directional communication is possible.
18.
Which of the following devices does not have a mac-address?
Correct Answer
D. None of the above
Explanation
All of the devices mentioned in the options (access points, switches, routers) have a MAC address. A MAC address is a unique identifier assigned to network interfaces for communication on a network. Therefore, the correct answer is "None of the above" as all the mentioned devices have a MAC address.