CCNA 200-125 Exam: NTP Questions With Answers

CCNA 200-125 Exam: NTP Questions With Answers
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  1. Which NTP command configures the local device as an NTP reference clock source?
    • A. ntp peer
    • B. ntp broadcast
    • C. ntp master*
    • D. ntp server

    Show (Hide) Explanation/Reference
    From a Cisco perspective, getting the clock from an Internet time source and/or from a local timing device both require the same command (ntp server). To have a specific network device consider itself as a reference clock source, another command is used (ntp master)

    For example, the command

    Router(config)#ntp server 192.168.1.1

    configures the local device to use a remote NTP clock source from 192.168.1.1 while the command:

    Router(config)#ntp master 1

    configures the local device as a NTP reference clock source with stratum of 1.

    Reference: http://www.pearsonitcertification.com/articles/article.aspx?p=2141272

  2. What command is used to configure a switch as authoritative NTP server?
    • A. ntp master 3 *
    • B. ntp peer IP
    • C. ntp server IP
    • D. ntp source IP

    Show (Hide) Explanation/Reference
    An Authoritative NTP Server can distribute time even when it is not synchronized to an existing time server. To configure a Cisco device as an Authoritative NTP Server, use the ntp master [stratum] command.
  3. Which value indicates the distance from the NTP authoritative time source?
    • A. priority
    • B. location
    • C. layer
    • D. stratum*
  4. Which NTP type designates a router without an external reference clock as an authoritative time source?
    • A. server
    • B. peer
    • C. master*
    • D. client
  5. Which command can you enter to configure the switch as an authoritative NTP server with a site id: 13999902?
    • A. Switch(config)#ntp master 3 *
    • B. Switch(config)#ntp peer 193.168.2.2
    • C. Switch(config)#ntp server 193.168.2.2
    • D. Switch(config)#ntp source 193.168.2.2

    Show (Hide) Explanation/Reference
    An Authoritative NTP Server can distribute time even when it is not synchronized to an existing time server. To configure a Cisco device as an Authoritative NTP Server, use the ntp master [stratum] command.
  6. Which two command can you enter to display the current time sources statistics on devices? (Choose two)
    • A. show ntp associations*
    • B. show clock details
    • C. show clock
    • D. show how time
    • E. show ntp status*

    Show (Hide) Explanation/Reference
    Maybe the “current time sources” here mention about the status of the clock source. In the below output, the “show ntp associations” command reveals the IP address of the clock source (which is 209.65.200.226), the stratum (st) of this reference clock…

    R1#show ntp associations
          address         ref clock     st  when  poll reach  delay  offset    disp
    *~10.1.2.1         209.65.200.226    9   509    64  200    32.2   15.44  16000.
     * master (synced), # master (unsynced), + selected, - candidate, ~ configured

    Below is the output of the “show ntp status” command. From this output we learn that R1 has a stratum of 10 and it is getting clock from 10.1.2.1.

    R1#show ntp status
    Clock is synchronized, stratum 10, reference is 10.1.2.1
    nominal freq is 250.0000 Hz, actual freq is 249.9987 Hz, precision is 2**18
    reference time is D5E492E9.98ACB4CF (13:00:25.596 CST Wed Sep 18 2013)
    clock offset is 15.4356 msec, root delay is 52.17 msec
    root dispersion is 67.61 msec, peer dispersion is 28.12 msec

    For more information about these two commands, please read at: http://www.cisco.com/c/en/us/support/docs/ip/network-time-protocol-ntp/116161-trouble-ntp-00.html

    In fact this question is unclear, but other answers are surely not correct.

  7. Which three commands are required to enable NTP authentication on a Cisco router? (Choose three)
    • A. ntp peer
    • B. ntp max-associations
    • C. ntp authenticate*
    • D. ntp trusted-key*
    • E. ntp authentication-key*
    • F. ntp refclock

    Show (Hide) Explanation/Reference
    + The “ntp authenticate” command is used to enable the NTP authentication feature (NTP authentication is disabled by default).

    + The “ntp trusted-key” command specifies one or more keys that a time source must provide in its NTP packets in order for the device to synchronize to it. This command provides protection against accidentally synchronizing the device to a time source that is not trusted.

    + The “ntp authentication-key” defines the authentication keys. The device does not synchronize to a time source unless the source has one of these authentication keys and the key number is specified by the “ntp trusted-key number” command.

  8. Which command can you enter to verify that a router is synced with a configured time source?
    • A. show ntp authenticate
    • B. ntp associations
    • C. ntp server time
    • D. ntp authenticate
    • E. show ntp associations*

    Show (Hide) Explanation/Reference
    In the below output, the “show ntp associations” command reveals the IP address of the clock source (which is 209.65.200.226), the stratum (st) of this reference clock and if a router is synced with the configured time source (in this case R1 is synchronized with 10.1.2.1, presented by a “*”).

    R1#show ntp associations
          address         ref clock     st  when  poll reach  delay  offset    disp
    *~10.1.2.1         209.65.200.226    9   509    64  200    32.2   15.44  16000.
     * master (synced), # master (unsynced), + selected, - candidate, ~ configured


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