NTP and PTP

Question 1

What port is used by NTP?

Answer 1

UDP 123

Question 2

What services on a Cisco router could be affected by NTP being inaccurate?

Answer 2

• Certificates
• Log Files
• VPN encryption keys
• Password expirations

Question 3

What purpose does Stratum serve in NTP?

Answer 3

It defines which NTP source should be most preferred when multiple sources exist. Lowest is best.

Question 4

In NTP, which “Stratum” is considered best?

Answer 4

Stratum 0

Question 5

What is the command to manually set the time on a router?

Answer 5

From privileged exec mode!

R1# clock set hh:mm:ss

Question 6

What is the command to set the time-zone on a router?

Answer 6

R1(config)# clock timezone NAME {offset}

example: R1(config)# clock timezone EASTERN -5

Question 7

What is the command to make a router the main NTP source?

Answer 7

R1(config)# ntp master {stratum-number}

Question 8

What is the command to set a NTP source for a router?

Answer 8

R1(config)# ntp server {ip-address}

NOTE: Multiple NTP servers can be set

Question 9

What is the command to set daylight savings time on a router?

Answer 9

R1(config)# clock summer-time NAME {many options [ ] [ ]}

Question 10

What are NTP peers?

Answer 10

When a couple of NTP devices point to each other for NTP redundancy to keep each other’s clocks in sync in the event that external NTP sources become unreachable.

Question 11

What is the command to set a NTP peer?

Answer 11

R1(config)# ntp peer {ip_address}

Question 12

What is PTP?

Answer 12

Precision Time Protocol (PTP) is defined in IEEE 1588 as Precision Clock Synchronization for Networked
Measurements and Control Systems, and was developed to synchronize the clocks in packet-based networks
that include distributed device clocks of varying precision and stability. PTP is designed specifically for
industrial, networked measurement and control systems, and is optimal for use in distributed systems because
it requires minimal bandwidth and little processing overhead.