You can check which hosts are talking to your time server by using the monlist command of ntpdc, e.g. ntpdc -c monlist Please note that a maximum of 600 entries is supported with current versions of ntpdc. The protocol (or better: the contents of the return packets) used by ntpdc is not standardized, therefore it is recommended to only use ntpdc with a matching ntpd, i.e. both should have the same version number.
To get by this 600 entry limitation, many server operators run client statistics scripts, such as Wayne Schlitt’s ntp_clients and ntp_clients_stats scripts, which can be found at http://www.schlitt.net/scripts/ntp/index.html . They work very well, but can use quite a bit of system resources if your client counts are in the high thousands. Examples of these scripts in action can be found at:
ntpq -p
The character in the left margin indicates the fate of this peer in the clock selection process. The codes mean:
<sp> discarded due to high stratum and/or failed sanity checks;
“x” designated falsticker by the intersection algorithm;
“.” culled from the end of the candidate list;
“-” discarded by the clustering algorithm;
“+” included in the final selection set;
“#” selected for synchronization but distance exceeds maximum;
“*” selected for synchronization;
“o” selected for synchronization, PPS signal in use.
