思科认证考试（ＣＣＮＡ）考试模拟题２０—３９及答案

CCNA试题20-39答案

20. [TxNx] If Host A sends a packet to Host B over token ring, and Host B is not active: 

a) The packet will time out. 
b) The packet will be removed by Host A. 
c) The NVRAM of Host B will remove the packet. 
d) The packet will "die" when it reaches the terminator. 
e) The packet will be removed by the token monitor. 

Answer 
b) The packet will be removed by Host A. 

21. [TxNx] If Host A sends a packet to Host B over token ring: Host A dies after transmitting, and Host B is not active: 

a) The packet will time out. 
b) The packet will be removed by Host A. 
c) The NVRAM of Host B will remove the packet. 
d) The packet will "die" when it reaches the terminator. 
e) The packet will be removed by the Active monitor. 

Answer 
e) The packet will be removed by the Active monitor. 

22. [FxNx] BECN and FECN are: 

a) Used to provide keepalives in a Frame Relay environment 
b) Used to provide error checking in a Frame Relay environment 
c) Used to provide congestion information in a Frame Relay environment 
d) Used to provide flow control parameters in a Frame Relay environment 
e) BECN and FECN are not used in a Frame Relay environment. 

Answer 
c) Used to provide congestion information in a Frame Relay environment 

The following are definitions of each: 

Backward Explicit Congestion Notification (BECN) - Bit set by a frame relay network in frames traveling in opposite direction of frames encountering a congested path. DTE receiving frames with the BECN bit set can request higher level protocols take flow control action. 

Forward Explicit Congestion Notification (FECN) - Bit set by a frame relay network to inform DTE receiving frame that congestion was experienced in the path from source to destination. 

23. [RxNx] Which of the following are benefits of a Link-State routing protocol? (Choose all that apply.) 

a) Allows the use of a more robust addressing scheme. 
b) Allows for a larger scalable network 
c) Reduces convergence time 
d) Allows "supernetting" 
e) All of the above. 

Answer 
e) All of the above 

24. [OxNx] Which of the following are reasons for the OSI model? 

a) Standardizes interfaces 
b) Allows modular engineering 
c) Facilitates learning and teaching 
d) All of the above. 

Answer 
d) All of the above 

25. [RxNx] Which of the following is NOT a ROUTING protocol: 

a) OSPF 
b) RIP 
c) IPX 
d) EIGRP 
e) NLSP. 

Answer 
c) IPX