[ntp:questions] ntpd not responding to sntp from industrial controller

[Danny Thomas]

We've got a RedLion industrial controller which uses SNTP but
doesn't seem to receive a response from either an AD domain
controller or from ntpd 4.2.7p136 on linux.

tcpdump shows the packets arriving but no response is sent.

I'm not sure of the best way to debug this so tried
  root at kolanut# /opt/ntp/bin/ntpd -g -D 100 2>&1 | grep 10.24.33.98
  read_network_packet: fd=23 length 52 from 10.24.33.98
  receive: at 1 130.102.2.123<-10.24.33.98 flags 19 restrict 190
  receive: at 1 130.102.2.123<-10.24.33.98 mode 3 keyid 00000000 len 52 auth 3

Nearly all the fields are ignored, so what's causing ntpd
not to respond ?  Key ID ?, stratum of 0 as KOD ?


REQUEST FROM RED-LION as displayed in wireshark
====================================================
Network Time Protocol
  Flags: 0x1b
    00.. .... = Leap Indicator: no warning (0)
    ..01 1... = Version number: NTP Version 3 (3)
    .... .011 = Mode: client (3)
  Peer Clock Stratum: unspecified or unavailable (0)
  Peer Polling Interval: invalid (0)
  Peer Clock Precision: 1.000000 sec
  Root Delay:    0.0000 sec
  Root Dispersion:    0.0000 sec
  Reference Clock ID: NULL
  Reference Clock Update Time: NULL
  Originate Time Stamp: NULL
  Receive Time Stamp: NULL
  Transmit Time Stamp: Jul 18, 2011 07:56:18.504990 UTC
  Key ID: 00000000


REQUEST FROM LINUX SNTP UTILITY
====================================================
Network Time Protocol
  Flags: 0x1b
  00.. .... = Leap Indicator: no warning (0)
  ..01 1... = Version number: NTP Version 3 (3)
  .... .011 = Mode: client (3)
  Peer Clock Stratum: secondary reference (15)
  Peer Polling Interval: 8 (256 sec)
  Peer Clock Precision: 1.000000 sec
  Root Delay:    0.0000 sec
  Root Dispersion:    0.0000 sec
  Reference Clock ID: 0.0.0.0
  Reference Clock Update Time: NULL
  Originate Time Stamp: NULL
  Receive Time Stamp: NULL
  Transmit Time Stamp: Jul 18, 2011 09:17:32.544954 UTC