Ccna certification Practice Tests

278

 

Appendix 

■

  Answers to Practice Test Questions

 159.  B.  The command 

ipconfig /all will display the generic information of IP, subnet mask, 

and gateway. It will also display the DHCP server that configured the client with an IP 

address. The standard 

ipconfig command will give you brief information, but not the 

DHCP server. The 

ipconfig /showclassid command will display the class information 

reported to the DHCP server. The 

ipstatus command is not a valid command, and 

therefore, it is not the correct answer.

 160.  C.  The DHCP server is not configured properly. When a Windows client configures itself 

with an IP address of 169.254.x.x, it is using APIPA, or Automatic Private IP Addressing 

(link-local addressing). It is highly unlikely that anyone would configure an APIPA scope, 

since it is used in the absence of a DHCP server. It is also highly unlikely that you would 

configure a client with a static IP address in the APIPA range. DHCP servers cannot be 

configured for APIPA.

 161.  A.  802.11 uses a contention method of Carrier Sense Multiple Access/Collision 

Avoidance. 802.11 implements a Request-to-Send/Clear-to-Send mechanism that avoids 

collisions. Ethernet uses a contention method of Carrier Sense Multiple Access/Collision 

Detection. Both Direct-Sequence Spread Spectrum (DSSS) and Orthogonal Frequency 

Division Multiplexing (OFDM) are wireless modulations used to transmit data.

 162.  C.  In the 2.4 GHz spectrum for 802.11, there are three non-overlapping channels: 

1, 6, and 11, each of which is 22 MHz wide. Although channel 14 technically is non-

overlapping, it is only allowed in Japan. All of the other options are incorrect.

 163.  D.  The 802.11ac protocol will be least likely to overlap the wireless channels the tenants 

are using. The 802.11ac protocol uses the 5 GHz wireless frequency spectrum. The 5 GHz 

spectrum defines 24 non-overlapping wireless channels. The 2.4 GHz spectrum defines 11 

channels, but only 3 of them are non-overlapping. Although 802.11n operates on 2.4 GHz 

and 5 GHz, 802.11ac only operates on 5 GHz. Therefore, 802.11ac will have the least 

likely overlap of current channels. 802.11b and 802.11g operate solely on the 2.4 GHz 

spectrum.

 164.  B.  Wired Equivalent Privacy (WEP) uses either 40- or 104-bit encryption; it also uses 

a 24-bit initialization vector (IV) to randomize each session. The encryption and IV 

combined, WEP advertises encryption strength of 64-bit or 128-bit. All Protected Access 

(WPA) variants use a variety of other mechanisms, but they do not use initialization 

vectors.

 165.  D.  WPA2 Enterprise does not use a pre-shared key (PSK) for authentication. In lieu of a 

PSK, WPA2 Enterprise uses certificates to authentication users. WPA, WPA2, and WEP 

use a pre-shared key for authentication.

 166.  C.  The 5 GHz band for 802.11 a/n/ac has 24 non-overlapping channels. The 2.4 GHz 

band for 802.11 b/g/n has only 3 non-overlapping channels. If the clients are compatible 

with 802.11 a/n/ac, it is desirable to use 5 GHz. 2.4 GHz goes further than 5 GHz; 

therefore, 5 GHz should not be used when distance is a concern. 5 GHz will not allow 

more clients to join the wireless access point (WAP). There is the same amount of 

interference on both 2.4 GHz and 5 GHz.

---

Chapter 1: Network Fundamentals (Domain 1)