JN0-102 · Question #284
Two devices on an Ethernet segment sent frames at the same time causing a collision. Which two statements are true? (Choose two.)
The correct answer is A. Both devices stop transmitting, wait a random period of time, verify the wire is idle, and re-transmit. D. Both devices send a jam signal to notify all other devices of the collision. In an Ethernet collision, devices involved stop transmission, send a jam signal to alert others, and then employ a random backoff algorithm before attempting to retransmit their frames.
Question
Two devices on an Ethernet segment sent frames at the same time causing a collision. Which two statements are true? (Choose two.)
Options
- ABoth devices stop transmitting, wait a random period of time, verify the wire is idle, and re-transmit.
- BThe device with the lowest MAC address is permitted to retransmit first.
- CThe device with the lowest MAC address sends a jam signal to notify all other devices of the collision.
- DBoth devices send a jam signal to notify all other devices of the collision.
How the community answered
(33 responses)- A94% (31)
- B3% (1)
- C3% (1)
Why each option
In an Ethernet collision, devices involved stop transmission, send a jam signal to alert others, and then employ a random backoff algorithm before attempting to retransmit their frames.
Following a collision, both devices cease transmission, engage a random backoff timer to avoid immediate re-collision, and then listen for an idle wire before attempting to retransmit their data.
The retransmission order after a collision is determined by a random backoff timer, not by the MAC address of the devices.
All devices involved in an Ethernet collision send a jam signal; it is not dependent on a device's MAC address.
When an Ethernet collision occurs, all devices that detect the collision send a jam signal, a special pattern, to ensure all other stations on the shared medium are aware of the collision event.
Concept tested: CSMA/CD collision detection and resolution
Source: https://www.cisco.com/c/en/us/support/docs/lan-switching/ethernet/10570-41.html
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