NTP Server¶

The NTP (Network Time Protocol) server provides accurate time synchronization for network clients. It supports both standalone operation with a local reference clock and hybrid mode where it synchronizes with upstream servers while serving time to downstream clients.

Note

The NTP server is mutually exclusive with the NTP client in system configuration context.

Standalone Mode¶

Configure a standalone NTP server using only a local reference clock:

admin@example:/> configure
admin@example:/config/> edit ntp
admin@example:/config/ntp/> leave

When setting up NTP via the CLI the system automatically configures a local reference clock. The default stratum is 16 (unsynchronized), which is suitable for isolated networks. For production use, configure a specific stratum level:

admin@example:/config/> edit ntp
admin@example:/config/ntp/> set refclock-master master-stratum 10
admin@example:/config/ntp/> leave

Server Mode¶

Synchronize from upstream NTP servers while serving time to clients:

admin@example:/config/> edit ntp
admin@example:/config/ntp/> edit unicast-configuration 0.pool.ntp.org type uc-server
admin@example:/config/ntp/…/0.pool.ntp.org/type/uc-server/> set iburst true
admin@example:/config/ntp/…/0.pool.ntp.org/type/uc-server/> end
admin@example:/config/ntp/> edit unicast-configuration 1.pool.ntp.org type uc-server
admin@example:/config/ntp/…/1.pool.ntp.org/type/uc-server/> set iburst true
admin@example:/config/ntp/…/1.pool.ntp.org/type/uc-server/> end
admin@example:/config/ntp/> leave

The unicast-configuration uses a composite key with both address and type. Both hostnames and IP addresses are supported. The iburst option enables fast initial synchronization.

Peer Mode¶

In peer mode, two NTP servers synchronize with each other bidirectionally. Each server acts as both client and server to the other:

First peer:

admin@peer1:/config/> edit ntp
admin@peer1:/config/ntp/> edit unicast-configuration 192.168.1.2 type uc-peer
admin@peer1:/config/ntp/…/192.168.1.2/type/uc-peer/> end
admin@peer1:/config/ntp/> set refclock-master master-stratum 8
admin@peer1:/config/ntp/> leave

Second peer:

admin@peer2:/config/> edit ntp
admin@peer2:/config/ntp/> edit unicast-configuration 192.168.1.1 type uc-peer
admin@peer2:/config/ntp/…/192.168.1.1/type/uc-peer/> end
admin@peer2:/config/ntp/> set refclock-master master-stratum 8
admin@peer2:/config/ntp/> leave

This configuration provides mutual synchronization between peers. If one peer fails, the other continues to serve time to clients.

Note

The iburst and burst options are not supported in peer mode.

Peer Selection in Symmetric Mode¶

When both peers have the same stratum (as in the example above where both are stratum 8), NTP's clock selection algorithm uses the Reference ID as the tie-breaker. The Reference ID is typically derived from the peer's IP address when using a local reference clock.

This means the peer with the numerically lower IP address will be selected as the sync source by the other peer. In the example above:

peer1 (192.168.1.1) has a lower Reference ID
peer2 (192.168.1.2) will select peer1 as sync source

This behavior is deterministic and ensures stable clock selection. If you need a specific peer to be selected, configure it with a lower stratum level than the other peer.

Timing Configuration¶

Poll Intervals¶

Control how often the NTP server polls upstream sources:

admin@example:/config/ntp/> edit unicast-configuration 0.pool.ntp.org type uc-server
admin@example:/config/ntp/…/0.pool.ntp.org/type/uc-server/> set minpoll 4
admin@example:/config/ntp/…/0.pool.ntp.org/type/uc-server/> set maxpoll 10
admin@example:/config/ntp/…/0.pool.ntp.org/type/uc-server/> end

Poll intervals are specified as powers of 2: - minpoll 4 = poll every 2^4 = 16 seconds (minimum polling rate) - maxpoll 10 = poll every 2^10 = 1024 seconds (maximum polling rate) - Defaults: minpoll 6 (64 seconds), maxpoll 10 (1024 seconds)

Use shorter intervals (minpoll 2-4) for faster convergence in test environments or peer configurations. Use defaults for production servers.

Fast Initial Synchronization¶

The makestep directive is automatically configured with safe defaults (1.0 seconds threshold, 3 updates limit) when creating an NTP server. This is critical for embedded systems without RTC that boot with epoch time.

To customize the values:

admin@example:/config/ntp/> edit makestep
admin@example:/config/ntp/makestep/> set threshold 2.0
admin@example:/config/ntp/makestep/> set limit 1
admin@example:/config/ntp/makestep/> end

threshold - If clock offset exceeds this (in seconds), step immediately instead of slewing slowly
limit - Number of updates during which stepping is allowed. After this, only gradual slewing is used for security

With these defaults, a device booting at epoch time (1970-01-01) will sync to correct time within seconds instead of hours.

Monitoring¶

Check NTP server statistics:

admin@example:/> show ntp server
NTP SERVER CONFIGURATION
Local Stratum       : 10

SERVER STATISTICS
Packets Received    : 142
Packets Sent        : 142
Packets Dropped     : 0
Send Failures       : 0

NTP Stratum Levels¶

NTP uses a hierarchical system called stratum to indicate distance from authoritative time sources:

Stratum 0: Reference clocks (atomic clocks)
Stratum 1: Servers directly connected to stratum 0 (e.g., GPS receivers)
Stratum 2-15: Servers that sync from lower stratum (each hop adds one)
Stratum 16: Unsynchronized (invalid)

The default stratum (16) is not suitable for distributing time in isolated networks, so when setting up an NTP server remember to adjust this value. Use, e.g., 10, this is a safe, low-priority value that ensures clients will prefer upstream-synchronized servers (stratum 1-9) while still having a fallback time source in isolated networks.