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Table of Contents
Public NTP Servers
REMEMBER : Do NOT use burst or iburst against public NTP servers unless they are announced they accept it (e.g. don't use it against *.ntp.org servers). More details hre.
- There is a dedicated page to general NTP.
- There is a dedicated page to Infoblox NTP.
pool.ntp.org
In most cases it's best to use pool.ntp.org to find an NTP server (or 0.pool.ntp.org, 1.pool.ntp.org, etc if you need multiple server names). The system will try finding the closest available servers for you. (source)
The number of active service in the geographic regions can be found here.
For the following list of NTP pools, you can use the following and/or prefix 0. or 1. or 2. or 3. to the FQDN
- pool.ntp.org
- africa.pool.ntp.org (54)
- asia.pool.ntp.org (282)
- europe.pool.ntp.org (2784)
- north-america.pool.ntp.org (934)
- oceania.pool.ntp.org (126)
- south-america.pool.ntp.org (58)
- <country code>.pool.ntp.org (e.g. uk.pool.ntp.org)
- <distribution>.pool.ntp.org (e.g. ubuntu.pool.ntp.org. NOTE for these you need to prefix 0. or 1. or 2. or 3. to the FQDN)
NTP Servers
In addition to pool.ntp.org, there are several other publicly accessible NTP servers (some of which also appear in pool.ntp.org).
DO NOT configure your system to use leap-smearing NTP servers as well as non-leap-smearing NTP servers at the same time. e.g. do not combine Google NTP with Cloudflare NTP as they do not implement leap smearing. Smearing is used by Google, AWS, and Facebook NTP servers but not Cloudflare.
More information on Google's NTP offering can be found here. Google 'smear' a leap second over the course of the hour either side of the leap second. Do not mix NTP servers that 'smear' and NTP servers that do not 'smear'. Google uses its own NTP servers for its public DNS servers. If you cannot configure multiple servers, time.google.com will automatically select an appropriate Google server nearby.
More specific are:
- ntp0.ja.net (Stratum 1)
- ntp1.npl.co.uk (Stratum 2)
- time.cloudflare.com (Stratum 3)
List of Stratum 1 servers
National Physics Laboratory hosts two public “Stratum 2” servers. This means their servers sync directly to atomic clocks.
| Operator | Server FQDN | Server IP | Stratum | RefID | Source Type or FQDN | Delay | Location | Supports iBurst |
|---|---|---|---|---|---|---|---|---|
| Cloudflare | time.cloudflare.com | 162.159.200.1 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.080 | UK | |
| Cloudflare | time.cloudflare.com | 162.159.200.123 | 3 | 10.21.8.19 | Internal Cloudflare? | 13.896 | UK | |
| Microsoft | time.windows.com | 51.145.123.29 | 3 | 25.66.230.5 | Internal Microsoft? | 13.896 | UK | |
| Zen Internet | ntp0.zen.co.uk | 212.23.8.6 | 2 | 195.66.241.3 | ntp1.linx.net | 11.642 | ||
| Zen Internet | ntp1.zen.co.uk | 212.23.10.129 | 2 | 85.199.214.99 | server1.quickdrivingtestcancellations.net | 16.948 | UK | |
| National Physics Laboratory | ntp1.npl.co.uk | 139.143.5.30 | 2 | 139.143.45.169 | ? | 16.457 | UK | |
| National Physics Laboratory | ntp2.npl.co.uk | 139.143.5.31 | 2 | 139.143.45.169 | ? | 17.329 | UK | |
| Manchester University | ntp2a.mcc.ac.uk | 130.88.202.49 | 2 | 193.62.22.66 | ntp0.ja.net | 22.581 | UK | |
| Manchester University | ntp2b.mcc.ac.uk | 130.88.203.13 | 2 | 130.88.203.13 | ntp0.ja.net | 22.282 | UK | |
| Manchester University | ntp2c.mcc.ac.uk | 130.88.200.6 | 2 | 193.62.22.66 | ntp0.ja.net | 22.135 | UK | |
| Manchester University | ntp2d.mcc.ac.uk | 130.88.212.143 | 2 | 193.62.22.74 | ntp1.ja.net | 22.771 | UK | |
| JANET, Harwell | ntp0.ja.net | 193.62.22.66 | 1 | .MSF. | MSF Radio Clock Receiver | 15.981 | UK | |
| JANET, Harwell | ntp1.ja.net | 193.62.22.74 | 1 | .MRS. | N/A | 26.042 | UK | |
| JANET, Harwell | ntp2.ja.net | 193.62.22.98 | 2 | 193.62.22.74 | ntp1.ja.net | 22.849 | UK | |
| JANET, Harwell | ntp3.ja.net | 193.62.22.90 | 1 | .PPS. | N/A | 26.305 | UK | |
| JANET, Harwell | ntp4.ja.net | 193.62.22.82 | 1 | .DCFa. | DCF77 | 17.528 | UK | |
| time.google.com | time1-time4 | 1 | Yes | |||||
| time1.google.com | 216.239.35.0 | 1 | .GOOG. | N/A | 20.393 | Yes | ||
| time2.google.com | 216.239.35.4 | 1 | .GOOG. | N/A | 20.399 | Yes | ||
| time3.google.com | 216.239.35.8 | 1 | .GOOG. | N/A | 20.514 | Yes | ||
| time4.google.com | 216.239.35.12 | 1 | .GOOG. | N/A | 22.899 | Yes | ||
| time.facebook.com | time1-time5 | 1 | Yes | |||||
| time1.facebook.com | 129.134.28.123 | 1 | .FB… | N/A | 25.595 | Yes | ||
| time2.facebook.com | 129.134.29.123 | 1 | .FB… | N/A | 16.803 | Yes | ||
| time3.facebook.com | 129.134.25.123 | 1 | .FB… | N/A | 12.037 | Yes | ||
| time4.facebook.com | 129.134.26.123 | 1 | .FB… | N/A | 18.341 | Yes | ||
| time5.facebook.com | 129.134.27.123 | 1 | .FB… | N/A | 16.546 | Yes | ||
| Apple | time.apple.com | 17.253.108.253 (and others) | 1 | .SHM. | 17.343 | Yes | ||
| Apple | time.euro.apple.com | 17.253.34.125 (and others) | 1 | .SHM. | 9.889 | Yes | ||
| Leo Bodnar Electronics | ntp1.leontp.com | 51.155.16.62 | 1 | .GPS. | N/A | 36.932 | UK | |
| Leo Bodnar Electronics | ntp5.leontp.com | 85.199.214.98 | 1 | .GPS. | N/A | 16.523 | UK | |
| Leo Bodnar Electronics | ntp6.leontp.com | 85.199.214.99 | 1 | .GPS. | N/A | 15.949 | UK | |
| Leo Bodnar Electronics | ntp7.leontp.com | 85.199.214.100 | 1 | .GPS. | N/A | 16.002 | UK | |
| Leo Bodnar Electronics | ntp8.leontp.com | 85.199.214.101 | 1 | .GPS. | N/A | 16.595 | UK | |
| Leo Bodnar Electronics | ntp9.leontp.com | 85.199.214.102 | 1 | .GPS. | N/A | 15.965 | UK | |
| Xentex IT Solutions | ntp.xtx.cloud | 81.133.66.177 | 1 | .PPS. | N/A | 24.301 | UK |