Cisco Certified Network Associate (CCNA) Practice Exam

What technology does collision detection and carrier sensing indicate for a network interface port?

1. This is an Ethernet port operating at full-duplex

2. This is an Ethernet port operating at half-duplex

3. This is a fiber optic port

4. This is a wireless network port

The correct answer is: This is an Ethernet port operating at half-duplex

Collision detection and carrier sensing are key characteristics of Ethernet technology when operating in a network environment. In networks utilizing half-duplex communication, devices share the same channel for both sending and receiving data, which means that only one device can transmit at a time. This setup makes it necessary for the devices to listen for traffic before sending, hence the use of carrier sensing. Collision detection is also implemented to identify when two devices have attempted to send data simultaneously, leading to a collision. When this happens, the devices stop transmitting and initiate a back-off period before attempting to resend the data. In contrast, full-duplex operations allow simultaneous sending and receiving of data, meaning neither collision detection nor carrier sensing is required, as there are no data collisions. Fiber optic ports typically use full-duplex as well, and wireless networks operate under different protocols, such as CSMA/CA, which do not align with the traditional collision detection found in wired Ethernet standards. Thus, the presence of collision detection and carrier sensing specifically indicates that the network interface port is operating in half-duplex mode.