NTP no server suitable for synchronization found

Michal Krzeminski · Apr 3, 2024, 2:06 PM

Hello, due to network reorganization i had to split existing NTP sources and created a standalone instance of NTP server on the pfSense v23.01.

The server itself seems to pull the time from outside servers OK:

Active Peer 194.146.251.101 .EXT. 1 u 22 64 377 1.407 +1.529 0.151
Candidate 80.50.231.226 .MRS. 1 u 19 64 377 0.715 +1.428 0.057
Candidate 194.146.251.100 .EXT. 1 u 39 64 377 1.482 +1.517 0.058
Outlier 213.135.57.60 229.30.220.210 2 u 15 64 377 1.329 +1.447 0.720
Outlier 195.187.245.55 .GPS. 1 u 31 64 377 1.918 +1.524 0.027

However, attempts to sync a client vary: i can sync a Windows machine (this particular was my work laptop with time source replaced from time.windows.com to my newly setup server), i can sync a Linux (Debian 5.10) using ntpdate by hand no problem as well:

ntpdate 10.140.0.1

3 Apr 10:01:07 ntpdate[237582]: adjust time server 10.140.0.1 offset +0.079342 sec

However, couple of hosts that synced with a time server before refuse to get synchronized. They run on FreeBSD and response is following:

ahmes.c.main:~# ntpdate 10.140.0.1
3 Apr 14:24:12 ntpdate[27920]: no server suitable for synchronization found

I have turned on packet capture during an attempt but can't make whats wrong with it; the request is received and response sent albeit with bad udp checksum (which may or may not be a problem...not sure).

Any help would be appreciated. Captured incoming request and response from pfSense ntpserver below.

14:24:10.840660 IP (tos 0x0, ttl 64, id 41655, offset 0, flags [DF], proto UDP (17), length 76)
10.142.0.50.123 > 10.140.0.1.123: [udp sum ok] NTPv4, length 48
Client, Leap indicator: clock unsynchronized (192), Stratum 0 (unspecified), poll 4 (16s), precision -6
Root Delay: 1.000000, Root dispersion: 1.000000, Reference-ID: (unspec)
Reference Timestamp: 0.000000000
Originator Timestamp: 0.000000000
Receive Timestamp: 0.000000000
Transmit Timestamp: 3921135850.627857999 (2024/04/03 14:24:10)
Originator - Receive Timestamp: 0.000000000
Originator - Transmit Timestamp: 3921135850.627857999 (2024/04/03 14:24:10)

14:24:10.840774 IP (tos 0xb8, ttl 64, id 27891, offset 0, flags [none], proto UDP (17), length 76)
10.140.0.1.123 > 10.142.0.50.123: [bad udp cksum 0x1596 -> 0x27d3!] NTPv4, length 48
Server, Leap indicator: (0), Stratum 2 (secondary reference), poll 4 (16s), precision -23
Root Delay: 0.001373, Root dispersion: 0.010162, Reference-ID: 194.146.251.101
Reference Timestamp: 3921135473.029547184 (2024/04/03 14:17:53)
Originator Timestamp: 3921135850.627857999 (2024/04/03 14:24:10)
Receive Timestamp: 3921135850.840705588 (2024/04/03 14:24:10)
Transmit Timestamp: 3921135850.840767366 (2024/04/03 14:24:10)
Originator - Receive Timestamp: +0.212847588
Originator - Transmit Timestamp: +0.212909366

stephenw10 · Apr 3, 2024, 4:53 PM

The checksum is probably because you have hardware checksum offloading enabled. But if it's not that would be a problem.

Those clients are set to sync against stratum 1 only? Seems unlikely.