Cisco CCNA mock exam questions sample test – Question 112

.Which type of network uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as an access method?

A. Token Ring
B. LocalTalk
C. 100VG-AnyLan
D. Ethernet

Correct Answer: D

Explanation:
Ethernet networks use CSMA/CD as an access method. In CSMA/CD, if a device wants to send a frame in the network, it first determines if the network is free. If the network is not
free, the node will wait before sending the frame into a network. If the network is free, it sends the frame; if another device sends a frame simultaneously then their signals or frames
collide. When the collision is detected, both packets wait for a random time before retrying.
The following statements are true regarding CSMA/CD:
CSMA/CD is required for shared collision domains, such as when hosts are connected via hubs. (Hubs are Layer 1 devices, and thus do not create collision domains.)
CSMA/CD networks normally operate in half-duplex mode, since in a shared collision domain, a host cannot send and receive data at the same time.
CSMA/CD is not required when connected to non-shared (private) collision domains, such as when hosts are connected to dedicated switch ports.
Switches create dedicated collision domains, so devices can operate in full-duplex mode.
Token Ring is incorrect because Token Ring uses token passing as the access method.
LocalTalk is incorrect because LocalTalk uses CSMA/CA (Collision Avoidance) as the access method.
100VG-AnyLan is incorrect because 100VG-AnyLan uses demand priority as the access method.
Objective:
LAN Switching Fundamentals
Sub-Objective:
Interpret Ethernet frame format
References:
Cisco > Internetworking Technology Handbook > Introduction to LAN Protocols > LAN Media-Access Methods