NTP Timing Based on GPS Clock

This chapter contains the following sections:

Configure NTP using GPS Time

From IOS XE release 17.6.1, you can set up Network Time Protocol (NTP) to use GPS time as the reference clock using the ntp refclock gps command.

The cellular modem-based GPS works only with cellular and not with the GPS on Dead Reckoning module.

Before you begin

Procedure

Step 1

Use the configure terminal command to enter global configuration mode.

Example:

Router# configure terminal

Step 2

Use the controller cellular comamnd to configure cellular location.

Example:

Router(config)# controller cellular 0/4/0

Step 3

Use the lte gps nmea command to enable National Marine Electronics Association (NMEA) streaming.

Example:

Router(config-controller)# lte gps nmea

Step 4

Use the end command to exit NMEA configuration mode and return to privileged EXEC mode.

Example:

Router(config-controller-nmea)# end

Step 5

Use the configure terminal command to enter global configuration mode.

Example:

Router# configure terminal

Step 6

Use the ntp refclock gps interface Cellular 0/4/0 commad to configure the NTP reference clock as GPS.

Example:

Router(config)# ntp refclock gps interface Cellular 0/4/0

Step 7

Use the exit command to exit from the configuration prompt.

Example:

Router(config)# exit

Step 8

(Optional) Use the show cellular cellualr slot gps command to view the GPS information.

Example:

Router# show cellular 0/4/0 gps
GPS Feature = enabled
GPS Mode Configured = standalone
Current Constellation Configured = gps
GPS Port Selected = Dedicated GPS port
GPS Status = GPS coordinates acquired
Last Location Fix Error = Offline [0x0]
Latitude = 50 Deg 36 Min 44.9907 Sec North
Longitude = 5 Deg 35 Min 12.0240 Sec East
Timestamp (GMT) = Tue Dec 17 17:06:05 2024

Fix type = 2D, Height = 64m
Satellite Info
----------------
Satellite #4, elevation 8, azimuth 329, SNR 31 *
Satellite #5, elevation 9, azimuth 88, SNR 37 *
Satellite #18, elevation 29, azimuth 170, SNR 48 *
Satellite #20, elevation 14, azimuth 54, SNR 30 *
Satellite #25, elevation 43, azimuth 111, SNR 40 *
Satellite #26, elevation 38, azimuth 292, SNR 34 *
Satellite #28, elevation 55, azimuth 227, SNR 44 *
Satellite #29, elevation 76, azimuth 67, SNR 38 *
Satellite #31, elevation 51, azimuth 281, SNR 29 *
Satellite #49, elevation 31, azimuth 180, SNR 46  **
Satellite #9, elevation 0, azimuth 0, SNR 0
Satellite #12, elevation 5, azimuth 106, SNR 0 *
Satellite #16, elevation 6, azimuth 288, SNR 0

Step 9

(Optional) Use the show ntp associations command to view the network time protocol associations.

Example:

Router# show ntp associations
  address         ref clock       st   when   poll reach  delay  offset   disp
x~127.127.5.1     .GPS.            0     58     64     3  0.000  -0.031 3938.4
*~45.87.78.35     244.220.219.218  2     51     64     3 13.985 495.081 64.377
 * sys.peer, # selected, + candidate, - outlyer, x falseticker, ~ configured

Step 10

(Optional) Use the show clock command to display the current time and clock details.

Example:


Router# show clock
17:12:56.870 UTC Tue Dec 17 2024

Step 11

(Optional) Use the debug ntp refclock command to troubleshoot the configuration.

Example:

Router# debug ntp refclock
*Sep 24 19:58:43.045 GMT: GPS: Poll Requested
*Sep 24 19:58:43.045 GMT: GPS (19:58:43.056 GMT Thu Sep 24 2020)
*Sep 24 19:58:43.045 GMT: Valid time rcvd from GPS: 2020/09/24 19:58:43.056 (frac = 0x0E560440)
*Sep 24 19:58:43.045 GMT: RTS poll timestamp (local clock) was 0xE31778F3.0B851ED8
*Sep 24 19:58:43.045 GMT: GPS timestamp is 0xE31778F3.0E560440
*Sep 24 19:58:43.045 GMT: NTP Core(NOTICE): ntpd PPM
*Sep 24 19:58:43.046 GMT: NTP Core(NOTICE): trans state : 5
*Sep 24 19:58:43.046 GMT: NTP Core(NOTICE): Clock is synchronized.