思科CCNA题目及答案
CCNA-Cisco-Chapter11
C1
1 An electrician has investigated your recent power problems and has suggested that they are caused by oscillation. What is the BEST solution to your problem?
Move the network server to another room
Replace UTP with fiber optic cable
* Rewire the electrical system
Fit commercial surge suppressors
2 What is another term that can be used to describe an Intermediate Distribution Frame (IDF)? work area (WA)
telecommunications outlet (TO)
main cross-connect (MCC)
* horizontal cross-connect (HCC)
3 Why is fiber optic cable commonly used as a network backbone between campus buildings?
It provides a less resistive path for electrical current to flow from one building to another
It enhances the signals at the physical layer
* It reduces the hazardous effects of electrical potential difference and lightning strikes
It is cheaper and easier to install than copper wire
4 Which of the following environmental specifications are recommended for a wiring closet ? Carpeted floor; tiled walls and an inward opening door
Wooden floor; brick walls and fluorescent lighting
Tiled floor; internal power outlets and a dropped ceiling
* Raised floor; wood covered walls and an internal light switch
5 What is one of the most significant causes of oscillatory noise problems on a power circuit? ??? Long wiring runs
School photocopiers
Locating power cables in elevator shafts
Air conditioners cycling on and off
6 What device is best used to minimize the effects of power line sags and brownouts?
A primary protection device
A surge suppressor
An optical isolator
* An uninterruptible power supply
7 What causes Electrostatic Discharge (ESD)?
Long power lines
Faulty electrical equipment
* An accumulation of static electricity
An increase in atmospheric humidity
8 Which of the following problems is caused by too high a humidity level in a wiring closet? Signal degradation
* Copper wire corrosion
Insulation failure
Power surges
9 What is the ideal room temperature and relative humidity at which a wiring closet should be
maintained?
* 21 degrees Celsius / 45 % relative humidity
21 degrees Fahrenheit / 45 % relative humidity
45 degrees Celsius / 21 % relative humidity
45 degrees Fahrenheit / 21 % relative humidity
10 What is the maximum length specified for 62.5/125μm multimode optical fiber run between the MDF and IDF?
90 m
800 m
2000 m
* 3000 m
11 What are the three components that make up an uninterruptible power supply?
* A battery, inverter and battery charger
A MOV, capacitor and diode
A generator, changeover circuit and server software
A circuit breaker, fuse and battery
12 Where does the horizontal cable extend?
From the main distribution frame in the wiring closet to the vertical cross connect in the intermediate distribution frame
From the telecommunications outlet in the work area to the horizontal cross-connect in the telecommunications closet
* From the patch panel in the point of presence to the backbone connection in the customer premises equipment
From the telecommunications outlet in the wiring closet to the conduit in the intermediate distribution frame
13 Which statement BEST describes the current flow in an electrical circuit with a DC source?
* It is constant over time
It varies over time
It increases with time
It decreases with time
14 Why are exposed metal components normally connected to the ground, or earth, pin of a power outlet?
The connection is needed to increase the resistance of the circuit to ground
* If an electrical fault occurs in the equipment, the connection will reduce the chance of shock Connecting the metal to ground makes it act like an insulator
The ground connection can act as an alternative path for controlled current flow if the neutral wire is disconnected
15 What is the term used to describe a problem in an electrical system between the hot, or live, wire and the neutral wire?
An isolated mode problem
A ground fault problem
* A common mode problem
A normal mode problem
16 What function does an electrical insulator perform?