2013 Latest Cisco DESGN (640-864) Exam 131-135

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QUESTION 131
ISDN is short for Integrated Services Digital Network. Under what category of WAN technologies does ISDN belong?
A. Cell-switched
B. Circuit-switched
C. Packet-switched
D. Leased lines
Correct Answer: B
Section: WAN VPN Explanation

Traditional WAN Technologies

When selecting a particular WAN technology, you should be familiar with the three major categories that represent traditional WANs:
Circuit switched. Data connections that can be brought up when needed and terminated when finished. Examples include ordinary public switched telephone network (PSTN) phone service, analog modems, and ISDN. Carriers reserve that call path through the network for the duration of the call.
Leased lines: A dedicated connection provided by the SP. These types of connections are point to point and generally more expensive. Time-division multiplexing (TDM)-based leased lines usually use synchronous data transmission.
Packet and cell switched. Connections that use virtual circuits (PVC/SVC) established by the SP. Packet- switched technologies include Frame Relay and cell-switched technologies such as ATM. ATM uses cells and provides support for multiple quality of service (QoS) classes. The virtual circuits are part of the shared ATM/Frame Relay SP backbone network. This gives the SP greater flexibility with its service offerings.
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 7 (Page 230)

QUESTION 132
As a network engineer, can you tell me accounting management on a network-management system allows a network manager to perform which function?
A. Assess the network’s effectiveness and throughput
B. Charge back to users for network resources
C. Performance management
D. Identify problem areas in the network
Correct Answer: B
Section: Management – Operations Explanation

QUESTION 133
Which address type is 225.10.1.1?
A. Unicast
B. Anycast
C. Multicast
D. Broadcast
Correct Answer: C
Section: IP addressing Explanation
Multicast addresses range from 224.0.0.1 to 239.255.255.255.
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 8

QUESTION 134
What is the length of the key used with Triple Data Encryption Standard (3DES)?
A. 64 bits
B. 168 bits
C. 128 bits
D. 56 bits
Correct Answer: B
Section: WAN VPN Explanation
In cryptography, Triple DES is the common name for the Triple Data Encryption Algorithm (TDEA or Triple DEA) block cipher, which applies the Data Encryption Standard (DES) cipher algorithm three times to each data block. Because of the availability of increasing computational power, the key size of the original DES cipher was becoming subject to brute force attacks; Triple DES was designed to provide a relatively simple method of increasing the key size of DES to protect against such attacks, without designing a completely new block cipher algorithm. Triple DES uses a “key bundle” which comprises three DES keys, K1, K2 and K3, each of 56 bits (excluding parity bits). The encryption algorithm is:
ciphertext = EK3(DK2(EK1(plaintext)))
I.e., DES encrypt with K1, DES decrypt with K2, then DES encrypt with K3.
Decryption is the reverse:
plaintext = DK1(EK2(DK3(ciphertext)))
I.e., decrypt with K3, encrypt with K2, then decrypt with K1.
Each triple encryption encrypts one block of 64 bits of data.
In each case the middle operation is the reverse of the first and last. This improves the strength of the algorithm when using keying option 2, and provides backward compatibility with DES with keying option 3.
The standards define three keying options:
Keying option 1 is the strongest, with 3 56 = 168 independent key bits.
Keying option 2 provides less security, with 2 56 = 112 key bits. This option is stronger than simply DES encrypting twice, e.g. with K1 and K2, because it protects against meet-in-the-middle attacks.
Keying option 3 is equivalent to DES, with only 56 key bits. This option provides backward compatibility with DES, because the first and second DES operations cancel out. It is no longer recommended by the National Institute of Standards and Technology (NIST), [5] and is not supported by ISO/IEC 18033-3.

QUESTION 135
Refer to the exhibit.
Which layer is the distribution layer?
A. Layer A
B. Layer B
C. Layer C
D. Layers A and B form a consolidated core and distribution layer
Correct Answer: B
Section: Design Explanation

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