Cisco Systems manual What is back off on an 802.3 network?, Answer A, B

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E is incorrect; its speed 10 times faster, not 100 times.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 44-45.

Q. 189

What is back off on an 802.3 network?

A.It is latency stored and forward switching.

B.It is the time used to token passing from machine to machine.

C.It is re transmission delay that is encountered when a collision occurs.

D.It the result of two nodes transmitting at the same time the frames from each transmitting device collide and are damaged.

Answer: C

Explanation: Backoff is done when a collision occurs. Those trying to transmit at the same time “back-off” and attempt to retransmit at a later time. A 802.3 network uses collision detection, so that the transmitters are notified of the collision. Then using a random calculated wait time, re-transmission occurs. By using a random wait time, hopefully both transmitter wait a different amount of time and do not attempt simultaneous transmission again.

Incorrect Answers:

A is incorrect; back off occurs after a collision has occurred and is not latency stored and forward switching. B is incorrect; has nothing to do with the passing of the token.

D is incorrect; back off is used to prevent another collision.

Steve McQuerry. Interconnecting Cisco Network Devices. (Cisco Press: 2000) pages 16-17.

Q. 190

Which are two steps are required to configure and apply standard access list on an interface? (Choose two)

A.Define and access list number and its parameter.

B.Enable an interface to become part of the access list group.

C.Define the number of access list to be supported on an interface.

D.Copy the access list definition to each interface that will support it.

Answer: A, B

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