Network Time Protocol (NTP)

Document revision 1.3 (04-Sep-2003)
This document applies to the MikroTik RouterOS V2.7

Table of Contents
Summary
Specifications
Related Documents
Description
NTP Client
- Property Description
- Example
NTP Server
Time Zone
- Example

Summary

NTP protocol allows synchronizing time among computers in network. The best is if there is internet connection available and local NTP server is synchronized to correct time source. List of public NTP servers is available: http://www.eecis.udel.edu/~mills/ntp/servers.html

Specifications

Packages required : ntp
License required : Any
Home menu level : /system ntp
Protocols utilized : NTP (RFC958)
Hardware usage: not significant

Description

Network Time Protocol (NTP) is used to synchronize time with some NTP servers in a network. MikroTik RouterOS privides both NTP client and NTP server.

NTP client synchronizes local clock with some other time source (NTP server). There are 4 modes in which NTP client can operate:

In unicast (Client/Server) mode NTP client connects to specified NTP server. IP address of NTP server must be set in ntp-server and/or second-ntp-server parameters. At first client synchronizes to NTP server. Afterwards client periodically (64..1024s) sends time requests to NTP server. Unicast mode is the only one which uses ntp-server and second-ntp-server parameters.
In broadcast mode NTP client listens for broadcast messages sent by NTP server. After receiving first broadcast message, client synchronizes local clock using unicast mode, and afterwards does not send any packets to that NTP server. It uses received broadcast messages to adjust local clock.
multicast mode acts the same as broadcast mode, only instead of broadcast messages (IP address 255.255.255.255) multicast messages are received (IP address 224.0.1.1).
manycast mode actually is unicast mode only with unknown IP address of NTP server. To discover NTP server, client sends multicast message (IP 239.192.1.1). If NTP server is configured to listen for these multicast messages (manycast mode is enabled), it replies. After client receives reply, it enters unicast mode and synchronizes to that NTP server. But in parallel client continues to look for more NTP servers by sending multicast messages periodically.

NTP Client

Submenu level : /system ntp client

[admin@MikroTik] > system ntp client print
	  enabled: no
	     mode: unicast
      primary-ntp: 0.0.0.0
    secondary-ntp: 0.0.0.0
	   status: stopped
[admin@MikroTik] >

Property Description

enabled (yes | no, default: no) - whether the NTP client is enabled
mode (unicast | broadcast | multicast | manycast, default: unicast) - NTP client mode
primary-ntp (IP address, default: 0.0.0.0) - specifies IP address of the primary NTP server
secondary-ntp (IP address, default: 0.0.0.0) - specifies IP address of the secondary NTP server

Statistics:

status (string) - status of NTP client:

stopped - NTP is not running (NTP is disabled)

error - there was some internal error starting NTP service. (please, try to restart (disable and enable) NTP service)

started - NTP client service is started, but NTP server is not found, yet

failed - NTP server sent invalid response to our NTP client. (NTP server is not synchronous to some other time source)

reached - NTP server contacted. Comparing local clock to NTP server's clock. (duration of this phase - approx 30 sec)

timeset - local time changed to NTP server's time. (duration of this phase - approx 30 sec)

synchronized - local clock is synchronized to NTP server's clock. NTP server is activated.

using-local-clock - using local clock as time source (server enabled while client disabled)

Example

To enable the NTP client to synchronize with the 159.148.60.2 server:

           status: reached
[admin@MikroTik] system ntp client> print
          enabled: yes
             mode: unicast
      primary-ntp: 159.148.60.2
    secondary-ntp: 0.0.0.0
           status: synchronized
[admin@MikroTik] system ntp client>

NTP Server

Submenu level : /system ntp server

[admin@MikroTik] > system ntp server print
      enabled: no
    broadcast: no
    multicast: no
     manycast: yes
[admin@MikroTik] >

Property Description

enabled (yes | no, default: no) - whether the NTP client is enabled
broadcast (yes | no, default: no) - whether NTP broadcast message is sent to 255.255.255.255 every 64s
multicast (yes | no, default: no) - whether NTP multicast message is sent to 224.0.1.1 every 64s
manycast (yes | no, default: yes) - whether NTP server listens for multicast messages sent to 239.192.1.1 and responds to them

Notes

NTP server activates only when local NTP client is in synchronized or using-local-clock mode.

If NTP server is disabled, all NTP requests are ignored.

If NTP server is enabled, all individual time requests are answered.

CAUTION! Using broadcast, multicast and manycast modes is dangerous! Intruder (or simple user) can set up his own NTP server. If this new server will be chosen as time source for Your server, it will be possible for this user to change time on Your server at his will.

Example

To enable NTP server to answer unicast requests only:

[admin@MikroTik] system ntp client> .. server print
      enabled: yes
    broadcast: no
    multicast: no
     manycast: no
[admin@MikroTik] system ntp client>

Time Zone

Submenu level : /system clock

[admin@MikroTik] > system clock print
	 time: aug/12/2002 18:31:20
    time-zone: +00:00
[admin@MikroTik] >

Notes NTP changes local clock to UTC (GMT) time by default

Example

Time zone is specified as a difference between local time and GMT time. For example, if GMT time is 18:00:00, but correct local time is 19:00:00, then time-zone has to be set to +1 hour:

[admin@MikroTik] > system clock set time-zone=1
[admin@MikroTik] > system clock print
	 time: aug/12/2002 19:31:57
    time-zone: +01:00
[admin@MikroTik] >

If local time is before GMT time, time-zone value will be negative. For example, if GMT is 18:00:00, but correct local time is 15:00:00, time-zone has to be set to -3 hours:

[admin@MikroTik] > system clock set time-zone=-3
[admin@MikroTik] > system clock print
	 time: aug/12/2002 15:32:20
    time-zone: -03:00
[admin@MikroTik] >