| Question 1 | Which layers of the OSI model are included in the lower layers ? -
A. Application, Session, Presentation -
B. Physical, Transport, Data Link, Network -
C. Data link, Physical, Network -
D. Session, Data Link, Physical |
| A1: | Answer B is correct. Over time Cisco has defined upper and lower layers differently. At one time Layer 4 (Transport) was considered transitional and not a part of either the upper or lower groupings. Then it was included in the lower layers, and today Cisco is moving away from the distinction of upper and lower layers entirely. Despite the changing definitions, the safe answer is B. Answer A is incorrect because Application, Session, and Presentation have always been a part of the upper layers. D cannot be correct because again, Session is part of the upper layers. C is incorrect because it would require Layer 4 to be either transitional or part of the upper layers. Layer 4 has never been considered one of the upper layers, and as this exam has just been completely revised, the old definition of Layer 4 as transitional is highly unlikely . |
| Question 2 | Which layer uses the Segment as a Protocol Data Unit (PDU)? -
A. Layer 3, Network -
B. Layer 1, Physical -
C. Layer 2, Data Link -
D. Layer 4, Transport |
| A2: | Answer D is correct. The Transport layer uses the segment as its Protocol Data Unit (PDU). The Physical layer uses Bits as a PDU while the Data Link uses Frames and the Network layer uses Packets. |
| Question 3 | Select three reasons why the industry uses a layered model. -
A. A layered model allows developers to change the features of one layer without affecting the other layers. -
B. Interoperability is guaranteed because developers are required to comply with the standards established by the OSI model. -
C. Troubleshooting is easier if a layered model is used by all parties. -
D. A layered model reduces the complexity of networking to more manageable sub-layers. |
| A3: | Answers A, C, and D are correct. Answer B is incorrect because compliance with the OSI model is voluntary. A developer can certainly improve the ease of interoperability by adhering to the OSI model, but in no way is a developer required to use the model. |
| Question 4 | Which of the following are upper layers of the OSI model? (Check all correct answers.) -
A. Layer 4 -
B. Network layer -
C. Session layer -
D. Presentation layer |
| A4: | Answers C and D are correct. The upper layers of the OSI model include Layer 7 (Application), Layer 6 (Presentation), and Layer 5 (Session). Answer A is incorrect because Layer 4 (Transport) sits between the upper layers and lower layers and is not considered a part of either. Answer B is incorrect because the Network layer (Layer 3) is part of the lower layers. |
| Question 5 | Which of the following are routable protocols? (Check all correct answers.) |
| A5: | Answers B, D, and E are correct. IPX from Novell, AppleTalk from Apple Computers, and TCP/IP all provide a place for a network address in their packets. RIP is used by routers to exchange path information and is considered a routing protocol, while Ethernet resides at Layer 2 and its frames have no place for a network address. |
| Question 6 | Which of the following could be a legitimate Media Access Control address? -
A. 192.168.254.3 -
B. 3FA2.4756.F9A3 -
C. A5514 -
D. C1.3A.77.5B |
| A6: | Answer B is correct. A complete MAC address is composed of three octets or 48 hexadecimal bits. Answers C and A are incorrect because they do not have three octets or 48 bits. Answer A is a valid TCP/IP address but again, does not have three octets or 48 hexadecimal bits required by a MAC address. |
| Question 7 | Which of the following are valid Protocol Data Units? (Check all correct answers.) -
A. Packet -
B. Frame -
C. Bits -
D. Segment |
| A7: | All of the answers are correct. The PDU for Layer 3 (Network) is the Packet. Frame is the PDU for Layer 2, Data Link. The Physical layer (Layer 1) uses Bits for a PDU, and Layer 4 (Transport) uses the Segment as a PDU. |
| Question 8 | Where is encapsulation used in the OSI model? -
A. All seven layers of the receiving station -
B. At peer layers of both the sending station and receiving station -
C. Only at the Network layer -
D. At the sending station |
| A8: | Answer D is correct. Answers A and B are incorrect because de-encapsulation is used at the receiving station. Although encapsulation is used at the network layer of the sending station, it is also used at other layers of the sending station and not at all at the receiving station. |
| Question 9 | What is the serial number of a network interface card that has been given an address of 0365.FF32.A673? |
| A9: | Answer D is correct. The last 24 bits (6 digits) of a network interface card's MAC address are a unique number (serial number) assigned by the manufacturer. The first 24 bits are a unique number assigned to the manufacturer as the manufacturer's identifier. |
| Question 10 | Which communications model best describes today's network operation? -
A. OSI -
B. TCP/IP -
C. OSPF -
D. DOD |
| A10: | Answer D is correct. The word "operation" is the key to this question. Answer A, OSI, is certainly the most commonly used model, but it is a theoretical model that rarely describes the actual operation of network or network equipment. TCP/IP is the most commonly used routable protocol, but it is not a communications model, which eliminates answer B. OSPF is a routing protocol, which eliminates answer C. Answer D, the Department of Defense Model (DoD), provided the specifications for TCP/IP. As such, it is the model which closest approximates how networks actually work today. |