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54 Cards in this Set
- Front
- Back
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WANs operate at what layers of the OSI Model?
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Data-link and Physical
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What is the largest WAN in the world?
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The Internet
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What is the size of an ATM cell?
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53 bytes (5 byte header and 48 byte payload)
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What are the 4 available WAN Connection Types?
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Leased Line, Circuit Switched, Packet Switched, Cell Switched
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Define Customer Premises equipment (CPE) and give an example.
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CPE is hardware leased or owned by customer (on customers' side of Demarcation Line). Ex. Router, Switch, firewall, PC
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What is the demarcation point?
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The Point between CPE and ISP hardware. This also marks point where responsibility ends and begins.
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What is the Local Loop?
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The local loop is the physical cable that extends from the demarc to the providers Central Office Switch.
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Define Central Office (CO)
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The CO is the WAN service provider's office where the local loop terminates and in which circuit switching occurs.
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What are WAN data link layer protocols?
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Data-link Encapsulations (Languages). Examples are HDLC, PPP, and Frame Relay
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What is the difference between Baseband and Broadband?
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Baseband - 1 carrier frequency is used. ex Ethernet
Broadband - multiple independent channels. AKA T1 or Cable. |
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What is Serial Transmission?
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Serial Transmission is a method of data transmission in which bits of data are transmitted sequentially over a single channel. WANs use serial transmission
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In WAN communications, what is Clocking?
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Clocking is the method used to syunchronoize data transmission among devices on a WAN. DCE end always determines clocking (Usually CSU/DSU)
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How many channels (time slots) are in a full point-to-point or Frame Relay T1 line?
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24 channels @ 64kbps each.
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WANs use multiplexing. What is Multiplexing?
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Multiplexing is a technology that enables multiple logical signals to be transmitted simultaneously across a single physical channel and then be combined into a single data channel at the source. This enables the signals to appear as one, combining the speeds of all channels.
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On what layer of the OSI model does multiplexing occur?
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Physical Layer
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What type of data can an ATM network transfer?
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Voice, Video, and Data. ATM is a cell switched network
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How many DS0s are bundled to create a T1 line?
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24 DS0s are bundled to create a T1 Line. (one per channel)
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Describe Packet-switched WAN Connections.
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Packet Switched connections use virtual circuits (VC) to provide end-to-end connectivity. Packet-switched connections are similar to leased lines, except that the line is shared by other customers. A packet knows how to reach its destination by the programming of switches. Frame Relay and X.25 are examples of a packet-switched connection.
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What are circuit-switched WAN Connections?
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Circuit-switched WAN connections are connections dedicated for only the duration of the call or the time required to transmit data. The telephone system is an example of a circuit-switched network.
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What type of WAN link is a Leased Line?
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A leased line is a point-to-point link that provides a single, preestablished WAN communication path from the customer to the remote network.
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Describe DSL
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A Digital Subscriber Line is a modem technology that uses existing twisted-pair telephone lines to transfer high-speed data. ADSL - Higher Downstream than Upstream. SDSL - same up and down.
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On what layer of the OSI model does DSL operate?
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DSL operates at the Physical Layer of the OSI model. It uses ATM, Ethernet, or PPP at the data link layer and IP on the Network layer.
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Define Inside Local Address
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The IP address assigned to a host on the inside, private network. This is usually a private IP
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Define Outside Local Address
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The IP address of an Outside host as it appears to the inside, private network
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Define Inside Global Address
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A registered, Internet-routable IP address that represents one or more inside local IP addressed to the outside world
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Define Outside Global Address
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The IP Address assigned to a host on the outside network by the host's owner. This is usually a routable IP.
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What is Overload NAT?
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Also known as PAT (port address translation). Many One-to-One Mapping.
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What are 3 benefits of NAT?
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-Eliminates readdressing overhead of hosts that require external access
-Conserves IP addresses through application port-level multiplexing -Hides the internal network, providing a small level of network security |
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How many internal hosts can be translated to one routable IP address through PAT?
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65,536
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What cisco command clears all the NAT mappings in the NAT Table?
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"Clear ip nat translation *"
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How do you view active NAT translations in the NAT Table?
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"show ip nat translations"
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Describe HDLC
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Default Encapsulation on cisco PTP routers
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What is the default encapsulation on a Cisco serial interface?
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HDLC
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How do you change a Serial's interface to HDLC?
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(Under Se Interface)
encapsulation hdlc |
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What is the Point to Point protocol (PPP)?
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PPP is an industry-standard protocol that provides router-to-router or router-to-host connections over synchronous and asynchronous links. It can be used to connect WAN links to other vendors' equpiment. It works with several network-layer protocols, such as IP and Internetwork Packet Exchange (IPX). PPP provides optional authentication through PAP, CHAP, or MS-CHAP
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What IOS command enables PPP on a Cisco router serial Interface?
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(Under SE)
Encapsulation ppp |
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What communication protocol allows you to connect your computer to the Internet using a standard telephone line, and can transmit multiple protocols?
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PPP Offers the following features
-Control of data link setup -Provides dynamic IP address assignment -Link configuration and link quality testing -Error Detection -Network-layer address negotiation and data compression -Supports several network-layer protocols |
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What features does LCP offer to PPP encapsulation?
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LCP offers Authentication, Callback, compression, error detection, and multilink to PPP encapsulation.
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What types of physical interfaces can you enable PPP on?
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-Asynchronous Serial
-Synchronous Serial -High-Speed Serial Interface (HSSI) |
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Name the WAN Encapsulation that can be configured on an asynchronous serial connection.
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PPP
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What two protocols are available for compression on PPP links?
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Stacker and Predictor. Predictor uses more memory and Stacker uses more CPU.
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What two methods of Authentication can be used with PPP links?
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PAP and CHAP
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Does CHAP use two-way or three-way handshake for authentication?
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CHAP uses 3 way
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If PPP is enabled on an interface, how do you view the LCP and NCP states of the Interface?
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Show Interface se X/X
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What is Frame Relay?
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An industry standard, Frame Relay is a switched data like layer protocol that uses virtual circuits to identify the traffic that belongs to certain routers. It provides dynamic bandwidth allocation and congestion control.
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Is Frame Relay Circuit or Packet-switched network?
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Packet switched netowork that creates virtual circuits (VC) between DTE devices on a network to enable bidirectional communication. These Virtual circuits can either be permanent or dynamic.
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In Frame Relay, what identifies a virtual circuit?
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The Data Link connection Identifier (DLCI) locally identifies a VC,
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Is a DLCI locally or globally significant?
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Locally
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Which encapsulation type is appropriate to use in a Frame Relay network that has routers from two different vendors?
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IETF
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List four devices used to connect to or used on a WAN.
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Router, WAN Switch, CSU/DSU, Communication Server.
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Four types of Multiplexing?
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-Time-division Multiplexing
-Frequency-division Multiplexing - Wave-division Multiplexing -Statistical-division Multiplexing |
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What are the two sublayers of PPP?
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Network control Protocol (NCP)
Link Control Protocol (LCP) |
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What three phases establish a PPP session?
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1.) Link Establishment: Each PPP device sneds LCP packets to configure and test the Link (Layer 1)
2.) Authentication Phase (optional) 3.) Network Layer protocol phase: PPP sends NCP packets to choose and configure one or more network layer protocols to be encapsulated and set of the PPP data link. |
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How do you enable PAP or CHAP on a Cisco Router?
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1.) Give the device a hostname
2.) Create a user ("username XXXXX password XXXXX") 3.) "int se0" -> "ppp authentication chap pap" |
