What is the purpose of a default gateway on a host ?
Answer: D
Correct answer: To forward traffic destined for networks outside the local one
When a host finds that a destination address does not lie on its own subnet, it sends the packet to the default gateway, normally the local router, to be routed onward. Assigning addresses is the work of DHCP and name resolution that of DNS.
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At which layer of the OSI model does a router operate ?
Answer: D
Correct answer: Network layer
A router forwards packets between networks on the basis of IP addresses, which is layer 3 work. A switch operates one layer below it using MAC addresses, and a hub lower still at the physical layer.
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Why does the data communication industry use the layered OSI reference model?
1.It divides the network communication process into smaller and simpler components, thus aiding component development, design, and troubleshooting.
2.It enables equipment from different vendors to use the same electronic components, thus saving research and development funds.
3.It supports the evolution of multiple competing standards and thus provides business opportunities for equipment manufacturers.
4.It encourages industry standardization by defining what functions occur at each layer of the model.
Answer: B
The main advantage of a layered model is that it can allow application developers to change aspects of a program in just one layer of the layer model's specifications.
Advantages of using the OSI layered model include, but are not limited to, the following:
It divides the network communication process into smaller and simpler components, thus aiding compo- nent development, design, and troubleshooting;
it allows multiple-vendor development through standardization of network components;
it encourages industry standardization by defining what functions occur at each layer of the model;
it allows various types of network hardware and software to communicate;
and it prevents changes in one layer from affecting other layers, so it does not hamper development.
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A receiving host has failed to receive all of the segments that it should acknowledge. What can the host do to improve the reliability of this communication session?
Answer: D
A receiving host can control the transmitter by using flow control (TCP uses Windowing by default). By decreasing the window size, the receiving host can slow down the transmitting host so the receiving host does not overflow its buffers.
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Which device forwards frames using MAC addresses and operates at the Data Link layer ?
Answer: C
Correct answer: Switch
A switch learns which MAC address sits on which port and forwards each frame only to that port, so it creates a separate collision domain per port. A hub simply repeats every signal to every port and does no addressing at all.
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Which fields are contained within an IEEE Ethernet frame header?
1.Source and destination MAC address
2.Source and destination network address
3.Source and destination MAC address and source and destination network address
4.FCS field
Answer: A
Correct answer: 1 and 4
An Ethernet frame carries the source and destination MAC addresses in its header and the frame check sequence at its end. Network addresses are not in the frame at all - they are in the IP packet the frame carries, one layer up. That separation is what allows the same IP packet to cross Ethernet, then a serial link, then Ethernet again, being re-framed at each hop.
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How to implement a network medium that is not susceptible to EMI. Which type of cabling should you use?
Answer: D
Correct answer: Fiber-optic cable
Fibre carries light rather than current, so it neither radiates interference nor picks any up, and it is completely immune to electromagnetic interference and to the ground potential differences that trouble copper between buildings. Coaxial cable and shielded twisted pair reduce interference; only fibre is genuinely unaffected by it.
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What are the decimal and hexadecimal equivalents for the binary number 10110111?
Answer: B
You must be able to take a binary number and convert it into both decimal and hexadecimal. To convert to decimal, just add up the 1s using their values. The values that are turned on with the binary number of 10110111 are 128 + 32 + 16 + 4 + 2 + 1 = 183. To get the hexadecimal equivalent, you need to break the eight binary digits into nibbles (4 bits), 1011 and 0111. By add- ing up these values, you get 11 and 7. In hexadecimal, 11 is B, so the answer is 0xB7.
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What are two purposes for segmentation with a bridge?
1.To add more broadcast domains.
2.To create more collision domains.
3.To add more bandwidth for users.
4.To allow more broadcasts for users.
Answer: B
Correct answer: 2 and 3
A bridge divides a network into separate collision domains, so stations on either side no longer contend with each other, which gives each segment its own share of the bandwidth. A bridge forwards broadcasts, so it does not divide the broadcast domain - that requires a router.
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Acknowledgments, sequencing, and flow control are characteristics of which OSI layer?
Answer: C
A reliable Transport layer connection uses acknowledgments to make sure all data is transmitted and received reliably. A reliable connection is defined by a virtual circuit that uses acknowledgments, sequencing, and flow control, which are characteristics of the Transport layer (layer 4).
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