ActualTests.Cisco.640-802.Exam.Q.and.A.08.15.08-DDU (1130589), страница 34
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The DHCP Discover message uses a special Layer 2 multicast address as thedestination address.D. The DHCP Discover message uses TCP as the transport layer protocol.E. The DHCP Discover message does not use a Layer 2 destination address.F. The DHCP Discover message does not require a transport layer protocol.Answer: A, BExplanation:DHCP uses UDP as its transport protocol. DHCP messages from a client to a server areActualtests.com - The Power of Knowing640-802sent to the DHCP server port (UDP port 67), and DHCP messages from a server to aclient are sent to the DHCP client port (UDP port 68).The client broadcasts aDHCPDISCOVER message on its local physical subnet. The DHCPDISCOVER messagemay include options that suggest values for the network address and lease duration.BOOTP relay agents may pass the message on to DHCP servers not on the same physicalsubnet.Each server may respond with a DHCPOFFER message that includes an availablenetwork address in the "ipaddr" field (and other configuration parameters in DHCPoptions).
Servers need not reserve the offered network address, although the protocol willwork more efficiently if the server avoids allocating the offered network address toanother client. The server unicasts the DHCPOFFER message to the client (using theDHCP/BOOTP relay agent if necessary) if possible, or may broadcast the message to abroadcast address (preferably 255.255.255.255) on the client's subnet.Incorrect Answers:C.
DHCP messages are broadcast to the "all hosts" address. IP multicast addresses are notused.D. UDP is used, not TCP.E. Since DHCP is used so that a client can obtain an IP address, a layer two destinationaddress must be used, as the layer 3 IP address does not yet exist on the client for thereturn traffic.F. DHCP, along with nearly every other type of traffic, requires the use of a transportlayer protocol.QUESTION 270:Which one of the following protocols uses both UDP and TCP ports for thetransport layer operation?A. FTPB. TFTPC. SMTPD.
TelnetE. DNSAnswer: EExplanation:TCP and UDP must use port numbers to communicate with the upper layers. Portnumbers keep track of different conversations crossing the network simultaneously.Originating-source port numbers are dynamically assigned by the source host, which willbe some number starting at 1024. 1023 and below are defined in RFC 1700, whichdiscusses what is called well-known port numbers.Virtual circuits that do not use an application with a well-known port number areassigned port numbers randomly chosen from within a specific range instead.
These portnumbers identify the source and destination host in the TCP segment. Only DNS usesboth UDP and TCP port 53.Actualtests.com - The Power of Knowing640-802QUESTION 271:Your Certkiller trainee Jack is curious about the function of a DHCP Server. Inparticular she wants to know how the process of dynamically assigning IP addressesto hosts work.
What should you tell her?A. Adresses are allocated after a negotiation between the server and the host to determinethe length of the agreement.B. Addresses are permanently assigned so that the hosts uses the same address at alltimes.C. Addresses are assigned for a fixed period of time. At the end of the period, a newrequest for an address must be made, and another address is then assigned.D. Addresses are leased to hosts. A host will usually keep the same address byperiodically contacting the DHCP server to renew the lease.E. None of the answer choices are correct.Answer: DExplanation:As you know, DHCP clients lease their IP addresses from DHCP servers.
When this leaseexpires, that IP address can no longer be utilized by the DHCP client. For that reason,DHCP client must periodically renew their IP address leases, preferably before the leasehas expired or is about to expire.TDHCP client passes through the renewing and rebinding states to renew its IP addresslease.Renewing state: The DHCP client first attempts to renew its lease when 50 percent ofthe lease time has expired.
To renew its lease, the DHCP client sends a directedDHCPREQUEST message to the DHCP server that provided the original lease. Ifrenewal is allowed, the DHCP server automatically renews the lease by responding witha DHCPACK message. This new IP address lease contains not only the original IPaddress if still available (or another IP address otherwise) but any TCP/IP clientconfiguration information.Rebinding state: If, for whatever reason, the DHCP client is not able to communicatewith the original DHCP server the executed its lease, it attempts another approach calledrebinding. Here the DHCP client attempts to contact any available DHCP server when87.5 percent of the lease time has expired.
The leasing process is akin to that detailedover the last several pages.Reference: http://www.windowsitlibrary.com/Content/329/08/5.htmlQUESTION 272:You work as a network technician at Certkiller .com. Study the exhibit carefully.Actualtests.com - The Power of Knowing640-802Based on the output shown above, what should you do to allow the Certkillerworkstations connected to the fastethernet0/0 interface to obtain an IP Address?A. Apply access-group 14 to interface FastEthernet 0/0B.
Add access-list 14 permit any any to the access list configurationC. Configure the IP address of interface FastEthernet 0/0 to 10.90.201.1D. Add an interface description to the FastEthernet 0/0 interface configuration.E. None of the aboveAnswer: CExplanation:According to question and exhibit:Router is configured for DHCP, which can provide the IP Address to host. And Host isconnected on fastethernet0/0 interface. IP Address is not assigned on host connectedinterface. Until assigning the same subnet of pool on interface, host unable to obtain IPAddress from Router.QUESTION 273:Network Topology Exhibit:Actualtests.com - The Power of Knowing640-802Certkiller 2 Fa0/0 exhibit:Certkiller 2 Fa0/1 exhibit:On this Certkiller network segment, the DHCP settings have recently been changedon the DHCP server and the client is no longer able to reach network resources.What should be done to correct this situation?A.
Issue the ipconfig command with the /release and /renew options in a commandwindow.B. Use the tracert command on the DHCP client to first determine where the problem islocated.C. Verify that the DNS server address is correct in the DHCP pool.D. Ping the default gateway to populate the ARP cache.E. Clear all DHCP leases on the router to prevent address conflicts.Answer: AExplanation:ipconfig is a command line utility available on all versions of Microsoft Windowsstarting with Windows NT. ipconfig is designed to be run from the Windows commandprompt.
This utility allows you to get the IP address information of a Windows computer.It also allows some control over active TCP/IP connections. ipconfig is an alternative tothe older 'winipcfg' utility. Using the release and renew options will force the PC to try toobtain an IP address again from the DHCP server.ipconfig /releaseThis option terminates any active TCP/IP connections on all network adapters andreleases those IP addresses for use by other applications. 'ipconfig /release" can be usedwith specific Windows connection names. In this case, the command will affect only thespecified connections and not all. The command accepts either full connection names orwildcard names.ipconfig /renewActualtests.com - The Power of Knowing640-802This option re-establishes TCP/IP connections on all network adapters.
As with therelease option, ipconfig /renew takes an optional connection name specifier.Both /renew and /release options only work on clients configured for dynamic (DHCP)addressing.Reference: http://compnetworking.about.com/od/workingwithipaddresses/a/ipconfig.htmQUESTION 274:Exhibit:You need to configure an IP address for workstation CertkillerA. Based on theinformation shown above, what IP address should be assigned to this host?A. 192.168.1.159/28B. 192.168.1.145/28C.
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