思科认证考试（ＣＣＮＡ）考试模拟题４０—５９及答案

58. [OxNx] When a Destination Service Access Point (DSAP) and Source Service Access Point (SSAP) are set to AA: 

a) All stations with AA contained in their MAC addresses would receive this frame.
b) All stations would receive this frame, because it acts like a broadcast.
c) The encapsulated protocol contained in the frame must be IP.
d) The encapsulated protocol contained in the frame is proprietary.
e) None of the above.

Answer
d) The encapsulated protocol contained in the frame is proprietary.

Refer to the following capture: 

The above capture is Cisco s proprietary Cisco Discovery Protocol (CDP). 

59. [RINx] What Cisco feature of RIP will reduce convergence time? 

a) Cisco uses full horizons as opposed to split horizons 
b) The hold down timer is not activated 
c) Event triggered updates are used 
d) Infinity is 10 instead of 16 
e) There is no Cisco feature to enhance the performance of IP RIP 

Answer
c) Event triggered updates are used 
Cisco uses triggered updates with IP RIP in addition to the periodic updates. Refer to the following outline that organizes the major routing protocols. Details of these routing protocols are will be addressed in later editions.

I. Interior Routing Protocols

A. Distance Vector 

RIP 
Cisco’s IGRP 
Novell’s IPX RIP 
Appletalk RTMP 
B. Link State 

OSPF 
IS-IS 
NLSP 
C. Hybrid 

Cisco’s EIGRP 
II. Exterior Routing Protocols

A. BGP4
B. EOP

To distinguish between Distance Vector and Link State I ask students to answer the following three questions:

What does the routing protocol talk ?
When does the routing protocol talk ?
Who does the routing protocol talk ?

Distance Vector talks the entire routing table to directly connected neighbors (less split horizon) periodically!

Link State talks just the state of the link to all neighbors when the state of the link changes. I like to use the following question in class to differentiate between distance vector and link state routing protocols.

What protocol are you using if your mother calls you every night to let you know that everyone in the family is alive ?

Suppose you make an agreement with your mother to call you just when there is a death in the family ?

Suppose Mom dies?