2013 Latest Cisco DESGN (640-864)Exam 191-195


Which is the maximum segment distance for Fast Ethernet over unshielded twisted-pair (UTP)?
A. 285 feet
B. 100 feet
C. 500 feet
D. 100 meters
Correct Answer: D
Section: Cabling Explanation
100BASE-TX is the predominant form of Fast Ethernet, and runs over two wire-pairs inside a category 5 or above cable (a typical category 5 cable contains 4 pairs and can therefore support two 100BASE-TX links). Like 10BASE-T, the proper pairs are the orange and green pairs (canonical second and third pairs) in TIA/EIA-568-B’s termination standards, T568A or T568B.
These pairs use pins 1, 2, 3 and 6. In T568A and T568B, wires are in the order 1, 2, 3, 6, 4, 5, 7, 8 on the modular jack at each end. The color-order would be green/white, green, orange/white, blue, blue/white, orange, brown/white, brown for T568A, and orange/white, orange, green/white, blue, blue/white, green, brown/white, brown for T568B.
Each network segment can have a maximum distance of 100 meters (328 ft). In its typical configuration, 100BASE-TX uses one pair of twisted wires in each direction, providing 100 Mbit/s of throughput in each direction (full-duplex). See IEEE 802.3 for more details. The configuration of 100BASE-TX networks is very similar to 10BASE-T. When used to build a local area network, the devices on the network (computers, printers etc.) are typically connected to a hub or switch, creating a star network. Alternatively it is possible to connect two devices directly using a crossover cable.
With 100BASE-TX hardware, the raw bits (4 bits wide clocked at 25 MHz at the MII) go through 4B5B binary encoding to generate a series of 0 and 1 symbols clocked at 125 MHz symbol rate. The 4B5B encoding provides DC equalization and spectrum shaping (see the standard for details). Just as in the 100BASE-FX case, the bits are then transferred to the physical medium attachment layer using NRZI encoding. However, 100BASE-TX introduces an additional, medium dependent sublayer, which employs MLT-3 as a final encoding of the data stream before transmission, resulting in a maximum “fundamental frequency” of 31.25 MHz. The procedure is borrowed from the ANSI X3.263 FDDI specifications, with minor discrepancies.

Which term accurately describes a specific measure of delay often used to describe voice and video networks?
A. Jitter
B. Flux
C. Latency
D. Reliability
Correct Answer: A
Section: Voice Video Explanation
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 14

Which layer is in charge of fast transport in the hierarchical network model?
A. Network
B. Distribution
C. Access
D. Core
Correct Answer: D
Section: Architecture Explanation

Table Cisco Enterprise Architecture Model

Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 2

SNMP is short for Simple Network Management Protocol. Which version or versions of SNMP specify security extensions as part of the protocol definition?
Correct Answer: C
Section: Management – Operations Explanation
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 15

What is the reason for switching preferred on shared segments?
A. Switched segments provide a collision domain for each host.
B. Switched segments provide a broadcast domain for each host
C. Shared segments provide a broadcast domain for each host.
D. Shared segments provide a collision domain for each host.
Correct Answer: A
Section: Design Explanation
Switches use specialized integrated circuits to reduce the latency common to regular bridges. Switches are the evolution of bridges. Some switches can run in cut-through mode, where the switch does not wait for the entire frame to enter its buffer; instead, it begins to forward the frame as soon as it finishes reading the destination MAC address. Cut-through operation increases the probability that frames with errors are propagated on the network, because it forwards the frame before the entire frame is buffered and checked for errors. Because of these problems, most switches today perform store-and-forward operation as bridges do. Switches are exactly the same as bridges with respect to collision-domain and broadcast-domain characteristics. Each port on a switch is a separate collision domain. By default, all ports in a switch are in the same broadcast domain. Assignment to different VLANs changes that behavior.
Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 3

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