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NTP Flashcards

Network Time Protocol

1
Q

What is the purpose of NTP

A

Synchronizing internal clocks across all devices on a network

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2
Q

What is the command to view the time in Cisco IOS

A

sh clock

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3
Q

What is the default timezone for Cisco devices

A

UTC

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4
Q

What is the command to view the time source on Cisco devices

A

sh clock detail

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5
Q

What is the default time source for Cisco devices

A

Hardware calendar

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6
Q

T/F: Hardware calendar is considered an authoritative source

A

F

Internal hardware clock of a device will drift over time, so it is not the ideal source

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7
Q

What does an asterisk in front of the output of sh clock mean?

A

The time is not considered authoritative

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8
Q

What is the most important reason to have an accurate time on a device?

A

Accurate log keeping for troubleshooting purposes

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9
Q

What is the command to view a device’s logs

A

sh logging

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10
Q

What is the command to manually configure the time on a Cisco device

A

clock set

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11
Q

What config mode do you need to be in for clock commands

A

Priviledged EXEC mode

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12
Q

What is the command to manually configure the hardware clock (aka calendar)

A

calendar set

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13
Q

T/F: You never want the calendar and the clock on a device synchronized

A

F

It is always a good idea for the calendar and the clock to be synchronized

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14
Q

What is the command to view a device’s hardware clock

A

sh calendar

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15
Q

What is the command to sync a device’s calendar to its clock time

A

clock update-calendar

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16
Q

What is the command to sync a device’s clock to the calendar time

A

clock read-calendar

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17
Q

What is the command to configure the time zone on a Cisco device

A

clock timezone

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18
Q

T/F: Timezone must be configured from global config mode since it is part of the device’s running config

A

T

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19
Q

T/F: Timezone must be configured from priviledged EXEC mode since it is not part of the device’s running config

A

F

Timezone is part of the running config and therefore has to be changed in global config mode

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20
Q

What is the command to enable daylight savings time automatic adjustment

A

clock summer-time (timezone) recurring (day to switch) (day to switch back)

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21
Q

NTP prevents us from having to manually configure _____

A

time on devices connected to the network

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22
Q

T/F: NTP doesn’t prevent device clocks from drifting and becoming out of sync

A

F

Part of NTP’s purpose is to provide clock synchronization across multiple devices

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23
Q

T/F: It is possible for a device to become an NTP server and an NTP client at the same time

A

T

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24
Q

Generally, NTP provides an accuracy of within _____ if the NTP server is in the same LAN

A

~1 millisecond

25
Q

Generally, NTP provides an accuracy of within _____ if the NTP server is over a WAN or the internet

A

~50 milliseconds

26
Q

What is the distance of an NTP server from the original reference clock referred to as

27
Q

The farther away from a reference clock, the higher the ______ of the server

28
Q

T/F: A reference clock is stratum 0 within the NTP hierarchy

29
Q

What is a reference clock?

A

A very accurate timekeeping device like an atomic clock or a GPS clock

30
Q

Describe a stratum 1 NTP server

A

An NTP server that is directly connected to a reference clock

31
Q

T/F: Cisco devices generally can’t get their time from a stratum 0 source

A

T

Cisco devices generally need to be connected to a stratum 1 or higher source

32
Q

T/F: A stratum 2 server is directly connected to a stratum 1 server and gets its time from the stratum 1 server

A

T

Stratum 2 servers get their time from stratum 1 servers

33
Q

T/F: A stratum 3 server is directly connected to a stratum 0 server and gets its time from the stratum 0 server

A

F

Stratum 3 servers get their time from a stratum 2 server

34
Q

What is the maximum stratum before an NTP server is considered unreliable

A

Stratum 15

35
Q

T/F: NTP devices can peer with devices at the same stratum to provide a more accurate time and redundancy

36
Q

When an NTP server is peered with another NTP server on the same stratum, it is referred to as being in ______

A

symmetric active mode

37
Q

T/F: A Cisco device cannot be in server, client, and symmetric active mode (all 3) at the same time

A

F

Cisco devices can operate in all 3 modes

38
Q

T/F: An NTP client cannot sync to multiple servers at the same time

A

F

An NTP client can sync to multiple NTP servers

39
Q

NTP servers which get their time directly from reference clocks are referred to as _____

A

primary servers

40
Q

Define an NTP primary server

A

One which is directly connected to a reference clock

41
Q

T/F: Stratum 1 servers can also be called secondary servers

A

F

They could be called primary servers

42
Q

NTP servers which get thier time from other NTP servers are called ____

A

Secondary servers

43
Q

Secondary servers operate in both ____ and ____ modes at the same time

A

Client, server

44
Q

NTP servers with stratum 2 and above are ____

A

secondary servers

45
Q

What is the command to add an NTP server to a Cisco device?

A

ntp server ip-address

46
Q

What is the command to manually have a Cisco device prefer a certain NTP server?

A

ntp server ip-address preferred

47
Q

What is the command to view NTP servers for a Cisco device?

A

sh ntp associations

48
Q

What is the command to get an overview of the NTP configuration on a Cisco device

A

sh ntp status

49
Q

T/F: NTP uses only the UTC time zone. To compensate, the time zone must be configured on the individual device

50
Q

What is the command to configure a router to update the hardware clock with the time learned via NTP

A

ntp update-calendar

51
Q

T/F: Normally, it is a bad idea to configure all devices to sync to public NTP servers in a small network

A

F

Best practice is to use public NTP servers for small networks. NTP servers are only needed for larger enterprise networks

52
Q

What is the command to change the source interface for NTP messages on a Cisco router?

A

ntp source interface

53
Q

Why is is best practice to configure the NTP source int as a loopback int?

A

Since loopbacks can’t physically fail, there is no possibility for an interface failure to cause a device to loose its NTP connection.

tl;dr reduces failure probability

54
Q

After manually configuring the system clock and issuing the ntp server 1.1.1.1 command, what should be done to complete a basic NTP client configuration?

A

Nothing, the basic configuration is complete.

55
Q

Issuing the ntp server command from global config mode enables ______

A

NTP static client mode

56
Q

R1 is connected to a subnet of NTP stratum 1 servers on its g0/0 interface. We want to configure R1 to receive its time from any NTP server on this connected subnet. What command should be issued?

A

ntp broadcast client on g0/0

57
Q

TOCK is an NTP stratum 2 server with the IP address 10.255.0.1

We want to configure R1 to synchronize its time from TOCK. What command should be issued to accomplish this?

A

ntp server 10.255.0.1

58
Q

R1 is configured to synchronize its time from TOCK, a stratum 2 NTP server. We want to configure R1 to act as an NTP server for its connected devices, while R1 still synchronizes with TOCK. What command should be issued to accomplish this?

A

ntp master 3

R1 gets its time from TOCK, a stratum 2 server, so it is therefore stratum 3

59
Q

Issuing the ntp peer command from global config mode enables _____

A

NTP symmetric active mode

CCNA (38 decks)

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