Network Time Protocol (NTP) and Junos: Keeping Things Synchronized

In the world of networking, time synchronization is crucial. It ensures that all devices in a network have the same time, which is essential for logging, troubleshooting, and security. This is where the Network Time Protocol (NTP) comes in. In this blog post, we will delve into the importance of NTP and how to configure it on Junos devices, a key topic for those studying for the JNCIS-ENT certification.

What is NTP?

NTP is a protocol designed to synchronize the clocks of computers over a network. It uses a hierarchical, semi-layered system of time sources, which are referred to as stratum. The stratum level defines the distance from the reference clock. A reference clock source that is directly attached to a time source (like a GPS receiver) is a stratum-1 device. A device that is synchronizing to a stratum-1 device is a stratum-2 device, and so on.

Why is NTP Important?

NTP is vital for a few reasons:

  1. Logging: Network devices generate logs for various events. These logs are timestamped, and if the time is not synchronized across devices, it can be challenging to correlate events happening across the network.
  2. Security: Some security mechanisms like Kerberos rely on time being synchronized across the network. If the time is not synchronized, these mechanisms might fail.
  3. Troubleshooting: When troubleshooting network issues, having a consistent time across all devices can help identify when an issue occurred and in what order events happened.

Configuring NTP on Junos Devices

Now, let's look at how to configure NTP on Junos devices. Here is a basic configuration:

set system ntp server
set system ntp server prefer

In this configuration, the Junos device is configured to synchronize its time with two NTP servers: and The 'prefer' keyword indicates that if both servers are reachable and providing valid time, the device should prefer the time provided by

You can verify the NTP configuration with the following command:

show ntp associations

This command will display the current NTP associations, including the IP address of the NTP server, the stratum level, and the status of the association.


NTP is a critical protocol in network engineering, and understanding it is essential for the JNCIS-ENT certification. It ensures that all devices in a network are synchronized, which is crucial for logging, security, and troubleshooting. Configuring NTP on Junos devices is straightforward, and verifying the configuration is just as easy. Remember, a network that keeps time together, works together!

In the next blog post, we will delve into more advanced NTP configurations, including authentication and serving time to other devices. Stay tuned!

Remember, the key to mastering any topic is practice. So, don't just read about NTP, configure it on a Junos device and experiment with different settings. Happy studying!

© Ben Jacobson.RSS