OpenNTPd server does not respond to a READSTAT command.

[cchildress]

The nagios / icinga plugin check_ntp_peer is intended to allow a monitoring server to confirm that a ntp server is healthy. It does this by sending a READSTAT opcode to the ntp server to request sync status and stratum info. I haven't been able to find any notes in the NTPv3 or NTPv4 RFC's that suggest this behavior has been deprecated.

It appears that OpenNTPd does not respond to this request. I've run a tcpdump from both the monitoring and the ntp servers and found that the ntp server does indeed receive the request, but does not respond.

Here is an example of the L4 segment and up of the outbound status request from one of my monitoring servers:

User Datagram Protocol, Src Port: 59515, Dst Port: 123
Network Time Protocol (NTP Version 2, control)
    Flags: 0x16, Leap Indicator: no warning, Version number: NTP Version 2, Mode: reserved for NTP control message
    Flags 2: 0x01, Response bit: Request, Opcode: READSTAT
    Sequence: 1
    Status: 0x0000
    AssociationID: 0
    Offset: 0
    Count: 0