Network Time

OPNsense ships with a standard NTPd server, which synchronizes time with upstream servers and provides time to connected clients.

A newly installed firewall comes with NTP enabled on all interfaces (firewall blocks all non LAN access in this case), forwarding queries to one of the X.opnsense.pool.ntp.org upstreams (X is any of 0,1,2,3).

General settings

In most cases the default setup is ready to use, below you will find some of the general options which can be configured.


Interface(s) Interfaces to bind to, when none is selected it listens to all
Time servers

Servers to use, comes with two toggles:

  • Prefer
    Marks the server as preferred.
  • Do not use
    Marks the server as unused, except for display purposes. The server is discarded by the selection algorithm.
Orphan mode Orphan mode allows the system clock to be used when no other clocks are available. The number here specifies the stratum reported during orphan mode and should normally be set to a number high enough to insure that any other servers available to clients are preferred over this server.
NTP graphs Enable RRD graphs of NTP statistics, which can be viewed in Reporting ‣ Health
Syslog logging Extend logging with peer and/or system messages
Statistics logging Enable statistical logging in /var/log/ntp, doesn’t come with a user interface
Access restrictions Within the access restriction row, you can set various options which limit the use of ntpd and in some cases instruct ntpd how to handle rejected clients.
Leap seconds You can manually supply ntpd with a leap seconds file, more detailed info on the contents of those files can be found here

Note

NTPs is disabled if no Time servers are configured. There is no separate enable/disable toggle.

GPS

If you own a gps receiver, which supports NMEA, you can use it as a reference clock and configure it in this section. For some brands settings are preconfigured, you can also use custom settings.

PPS

If your GPS receiver supports PPS (Pulse Per Second) output or you have a separate PPS signal available, you can configure the serial port to use along with some other settings here.

Status

The status page can be used to query the health of the upstream time sources, it shows the following characteristics.


Status Human readable status of the upstream
Server Upstream source
Ref ID Source IP address or kiss code:
Stratum NTP uses a hierarchical, semi-layered system of time sources (wikipedia) This field shows the stratum of the upstream source (lower usually means closer to the actual time source)
Type

Type of time source, one of:

  • u: unicast or manycast client
  • b: broadcast or multicast client
  • p: pool source
  • l: local (reference clock)
  • s: symmetric (peer)
  • A: manycast server
  • B: broadcast server
  • M: multicast server
When time in seconds, minutes, hours, or days since the last packet was received, or ‘-‘ if a packet has never been received
Poll poll interval in seconds
Reach reach shift register (octal), when set to 377 all 8 bits are set and thus no responses have been lost. Convert to bits to inspect which tries failed. (e.g. 257 –> 10101111 means the last four responses where received and two where lost within the last 8 tries)
Delay roundtrip delay in milliseconds
Offset offset time in milliseconds of the server relative to this host
Jitter indicates the difference, in milliseconds, between two samples