ActualTests.Cisco.640-802.Exam.Q.and.A.08.15.08-DDU (1130589), страница 4
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You are requiredto ensure that the web server is accessible from the Internet. The network usesprivate addressing, so an IP-to-registered address mapping is required.To do this, you enter the following command:Certkiller (config)# ip nat inside source static 192.168.2.1198.18.1.254You unsuccessfully try to ping the Internet from a PC host on the LAN.
During thetroubleshooting process, you enter the "show ip nat translations" command but theoutput is blank.What is the most likely cause of the problem?A. The keyword overload is missing from the command.B. The NAT pool must be defined first.C. An access list must be defined to create static NAT translations.D. The interfaces must be configured for NAT.E. None of the aboveAnswer: DExplanation:In order to successfully configure a static NAT translation, the interfaces must beconfigured for NAT, in addition to the global NAT command that was entered.
Therouter interface that lies on the inside part of the network must be defined using the "ipnat inside" command. Similarly, the WAN interface that is being used for the Internetconnection must be defined using the "ip nat outside" command.Incorrect Answers:A. In order to make an internal server reachable from the Internet, a static one to oneNAT entry must be configured for the server.
The keyword "overload" is used toconfigure many to one NAT, or PAT.B, C. This need not be done in order to create a static NAT entry. These steps aretypically done in setting up NAT so that inside LAN users can access the Internet viaNAT.Actualtests.com - The Power of Knowing640-802QUESTION 30:Which protocol below uses TCP port 443 at layer 4?A. HTMLB.
HTTPSC. TFTPD. TelnetE. SMTPF. None of the aboveAnswer: BExplanation:HTTPS is the secured version of the HTTP application, which normally uses 128 bit SSLencryption to secure the information sent and received on a web page. An example is abanking web site, or a trustworthy shopping web site that takes credit card information. Itis an application layer protocol which uses TCP port 443.Incorrect Answers:A. HTML is not a protocol.C.
TFTP uses UDP port 69.D. Telnet uses TCP port 23.E. SMTP uses TCP port 25.QUESTION 31:As a CCNA candidate, you will be expected to know the OSI model very well.Which of the following are associated with the application layer (layer 7) of the OSImodel? (Choose two)A. TCPB. TelnetC. FTPD. PingE. IPF. UDPAnswer: B, CExplanation:The application layer is the top layer of the OSI model and is used to describe the enduser applications that can be used over a network.Actualtests.com - The Power of Knowing640-802Layer Name ExamplesApplication (layer 7) Telnet, HTTP, FTP, WWW browsers, NFS, SMTP gateways,SNMPIncorrect Answers:A.
TCP resides at layer 4.D. ARP is a function of the data link layer, which is layer 2.E. IP is used at layer 3 (network layer).Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,ISBN 1-58720-094-5) Page 34.QUESTION 32:As the Certkiller network administrator, you are required to have a firmunderstanding of the OSI model. Why does the data communication industry usethe layered OSI reference model? (Choose two)A. It enables equipment from different vendors to use the same electronic components,thus saving research and development fundsB. It encourages industry standardization by defining what functions occur at each layerof the modelC.
It divides the network communication process into smaller and simpler components;thus aiding component development, design and troubleshootingD. It provides a means by which changes in functionality in one layer require changes inother layersE. It supports the evolution of multiple competing standards and thus provides businessopportunities for equipment manufacturersAnswer: B, CExplanation:The OSI (Open System Interconnection) reference model was created as a reference pointfor communications devices. A layered approach is used to segment the entiretelecommunications process into a series of smaller steps.A is correct because it encourages a level of standardization by encouraging thatfunctions be compared to known layers.
D is also correct because it allows engineers tofocus on the development, refining, and perfection of simpler components.QUESTION 33:You need to describe the various types of flow control to your co-workers. Which ofthe following are types of flow control that can be used in a network? (Choose three)A. Congestion avoidanceActualtests.com - The Power of Knowing640-802B. WindowingC. Cut-throughD. BufferingE.
Load BalancingF. Fast ForwardAnswer: A, B, DQUESTION 34:Which of the protocols below use TCP at the transport layer? (Select four)A. TFTPB. SMTPC. SNMPD. FTPE. HTTPF. HTTPSAnswer: B, D, E, FExplanation:SMTP (Simple Mail Transfer Profile for email), FTP (File Transfer Protocol), andHTTP/HTTPS (Hyper Text Transfer Protocol for internet) all use TCP because of thereliable delivery mechanism. SMTP uses TCP port 25, FTP uses TCP ports 20 and 21,HTTP uses TCP port 80, and HTTPS uses TCP port 443.Incorrect Answers:A, C: SNMP and TFTP use UDP as the transport mechanism. Generally speaking,protocols that use the keywords "trivial" or "simple" uses UDP, since connectionless,best effort delivery mechanism usually suffice.Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press,ISBN 1-58720-094-5) Page 163.QUESTION 35:Exhibit:The exhibit above displays the partial contents of an encapsulation header.Which of the following are true of the network traffic represented in this diagram?(Select three)Actualtests.com - The Power of Knowing640-802A.
This is a UDP headerB. This is an OSI layer 4 header.C. This is traffic from an FTP server.D. This is traffic from an Telnet client.E. The last PDU received in this session had a sequence number of 292735.Answer: B, C, EExplanation:As the header contains the sequence number and ACK number fields, it represents a TCPheader.
Choice B is correct as TCP works on Layer 4 i.e. Transport Layer.Source Port mentioned in the header is 21 which indicate it is FTP Traffic because FTPuses port 20 and 21 for data and control. So choice C is correct.The acknowledgment number refers to the sequence number of the last PDU received,which is 292735, making choice E also correct.QUESTION 36:Which fields are included in the TCP header? (Choose three).A. Source PortB. Acknowledgement NumberC. Request NumberD. Destination AddressE. WindowF.
DataAnswer: A, B, EExplanation:TCP header:Source Port: 16 bits.Destination Port: 16 bits.Sequence Number: 32 bits.The sequence number of the first data byte in this segment. If the SYN bit is set, thesequence number is the initial sequence number and the first data byte is initial sequencenumber + 1.Actualtests.com - The Power of Knowing640-802Acknowledgment Number: 32 bits.If the ACK bit is set, this field contains the value of the next sequence number the senderof the segment is expecting to receive.
Once a connection is established this is alwayssent.Data Offset: 4 bits.The number of 32-bit words in the TCP header. This indicates where the data begins. Thelength of the TCP header is always a multiple of 32 bits.Reserved: 3 bits.Must be cleared to zero.ECN, Explicit Congestion Notification: 3 bits.Added in RFC 3168.Control Bits: 6 bits.Window: 16 bits, unsigned.The number of data bytes beginning with the one indicated in the acknowledgment fieldwhich the sender of this segment is willing to accept.Checksum: 16 bits.This is computed as the 16-bit one's complement of the one's complement sum of apseudo header of information from the IP header, the TCP header, and the data, paddedas needed with zero bytes at the end to make a multiple of two bytes.Urgent Pointer: 16 bits, unsigned.If the URG bit is set, this field points to the sequence number of the last byte in asequence of urgent data.Options: 0 to 44 bytes.Options occupy space at the end of the TCP header.
All options are included in thechecksum. An option may begin on any byte boundary. The TCP header must be paddedwith zeros to make the header length a multiple of 32 bits.Data: Variable length.QUESTION 37:Acknowledgements, sequencing, and flow control are functions that are handled bywhich layer of the OSI model?A. Layer 5B. Layer 4C. Layer 7D.
Layer 6E. Layer 3F. Layer 2G. Layer 1Answer: BQUESTION 38:Actualtests.com - The Power of Knowing640-802A receiving host has failed to receive all of the segments that it should acknowledge.What can the host do to improve the reliability of this communication session?A. Start a new session using UDPB. Obtain a new IP address from the DHCP serverC. Use a different source port for the sessionD. Decrease the sequence numberE. Decrease the window sizeAnswer: EExplanation:A TCP window the amount of outstanding (unacknowledged by the recipient) data asender can send on a particular connection before it gets an acknowledgment back fromthe receiver that it has gotten some of it.For example if a pair of hosts are talking over a TCP connection that has a TCP windowsize of 64 KB (kilobytes), the sender can only send 64 KB of data and then it must stopand wait for an acknowledgment from the receiver that some or all of the data has beenreceived.
If the receiver acknowledges that all the data has been received then the senderis free to send another 64 KB.One way to improve the reliability of the TCP connection is to reduce the window sizethat the receiver needs to receive before sending an acknowledgement. However, this willreduce throughput as more segments and acknowledgements will need to be sent in orderto transfer the same amount of data.QUESTION 39:You have set up an Internet based FTP server, where people can upload anddownload files. In terms of the OSI model, what is the highest layer used during theFTP sessions.A. ApplicationB. PresentationC.
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