4.2 NTP Operating Flashcards
Configure and verify NTP operating in a client and server mode. (28 cards)
What is the primary function of Network Time Protocol (NTP)?
It synchronizes time across devices.
NTP ensures consistent timestamps across network devices, improving log accuracy and security functions.
What does a lower stratum number indicate about an NTP server’s accuracy?
Greater accuracy
In NTP (Network Time Protocol), a lower stratum number means the server is closer to the reference clock, making it a more precise time source.
How many servers can an NTP client use to synchronize time?
Multiple
An NTP client can connect to several servers to determine the most accurate time, rather than relying on a single source.
What is the purpose of the ‘ntp master’ command in NTP configuration?
It allows a device to act as an NTP server.
The ntp master command enables a device to serve time using its internal clock but does not prevent it from synchronizing with external servers.
What does the term ‘stratum’ refer to in NTP?
It describes the distance between a device and the reference clock.
Stratum levels indicate how close a time source is relative to the primary reference clock, with lower levels indicating closer proximity.
Which command displays NTP associations on a device?
‘show ntp associations’
This command provides detailed information about NTP servers associated with the device, including their addresses and polling intervals.
Which command shows the current date and time on a device?
‘show clock’
The ‘show clock’ command outputs the current date and time in a 24-hour format for the device.
What can happen if routers R1 and R2 do not synchronize their clocks?
Log messages may appear unrelated.
Differing timestamps across devices can complicate troubleshooting and event correlation.
What command is used to set the timezone on a router?
clock timezone {timezone} {offset}
This command configures the local timezone by specifying an offset from UTC.
What does the command ‘ntp master {stratum-level}’ do?
It sets the router as an NTP server with a defined stratum level.
The stratum-level parameter assigns a priority to the device as a time source. However, it does not override other NTP settings, meaning the router can still sync with external sources if allowed.
What command is used to configure a router as an NTP client?
ntp server {address | hostname}
This command enables the router to sync its clock with an external NTP server.
What is the significance of the stratum level in NTP?
Lower stratum means higher accuracy.
Stratum levels range from 1 (most accurate) to 15. Stratum 16 indicates an unusable clock.
True or False:
NTP clients can also act as NTP servers.
True
NTP clients can redistribute time to downstream devices, forming an NTP hierarchy.
Fill in the blank:
Before enabling NTP, it is important to set the device clock using ‘______ ______’.
clock set
Manually setting the clock prevents large time jumps when NTP first synchronizes.
What does a status of ‘synchronized’ indicate in NTP?
The client has adjusted its clock.
A synchronized NTP client has successfully matched its time to a server.
What command is used to verify NTP client status?
show ntp status
This command confirms synchronization state, stratum level, and reference clock details.
What is the purpose of the ‘clock summer-time’ command?
It configures daylight savings time.
This command adjusts the clock automatically during daylight saving transitions.
What does the stratum level indicate in NTP?
Accuracy of the reference clock.
Lower stratum levels indicate greater accuracy, with stratum 1 being the most precise.
What is the default stratum level for routers and switches in NTP?
8
The default NTP stratum level for Cisco devices is 8 unless manually configured.
What happens to devices that calculate their stratum as 16 in NTP?
It considers time data unreliable.
A stratum 16 device does not trust its time source and will not distribute time to clients.
What does the ntp master command do?
It configures a device as an authoritative NTP server.
The command allows a router to serve as an authoritative NTP source with a defined stratum level (1–15).
List ways routers can maintain NTP if external servers fail.
- Use ntp master as an internal time source.
- Synchronize with a local peer (ntp peer).
- Maintain previously learned time.
- Use a backup internal NTP server.
The ntp master command alone is not the only solution. Peer synchronization and fallback configurations help ensure time accuracy in case of external server failure.
True or False:
The ntp master command forces a device to use its own clock and ignore other sources.
False
The command allows the device to act as a time server but does not disable synchronization with external NTP servers unless additional restrictions are applied.
What is the benefit of using a loopback interface for NTP?
It ensures NTP stability.
A loopback interface remains active as long as the router is up, preventing disruptions due to physical interface failures.
