FWIW: I compiled the probe and couldn't find anything out of the ordinary: ./busybox evntp -6 -c 3 -w 4000 ntp0.testdns.nl RESULT { "dst_name":"ntp0.testdns.nl", "ttr":109.453445, "dst_addr":"2a02:2308:20:0:216:3eff:fe85:f45c", "src_addr":"2001:1c00:c081:ed00:201:c0ff:fe06:3551", "proto":"UDP", "af": 6, "li": "no", "version": 4, "mode": "server", "stratum": 1, "poll": 128, "precision": 1.19209e-07, "root-delay": 0, "root-dispersion": 0, "ref-id": "XFUN", "ref-ts": 3961497676.014892578, "result": [ { "origin-ts": 3961497975.998575211, "receive-ts": 3961497976.014892578, "transmit-ts": 3961497976.014945984, "final-ts": 3961497976.027197838, "rtt": 0.028570, "offset": -0.002033 }, { "poll": 256, "precision": 3.72529e-09, "ref-ts": 3961497676.041306019, "origin-ts": 3961497976.027345181, "receive-ts": 3961497976.041306019, "transmit-ts": 3961497976.041354656, "final-ts": 3961497976.051036835, "rtt": 0.023643, "offset": -0.002139 }, { "poll": 256, "precision": 1.49012e-08, "ref-ts": 3961497676.063885689, "origin-ts": 3961497976.051280022, "receive-ts": 3961497976.063885689, "transmit-ts": 3961497976.063924313, "final-ts": 3961497976.072422028, "rtt": 0.021104, "offset": -0.002054 } ] } ./busybox evntp -6 -c 1 ntp1.testdns.nl RESULT { "dst_name":"ntp1.testdns.nl", "ttr":479.530349, "dst_addr":"2a05:f480:1800:2898:5400:5ff:fe7c:8c82", "src_addr":"2001:1c00:c081:ed00:201:c0ff:fe06:3551", "proto":"UDP", "af": 6, "li": "no", "version": 4, "mode": "server", "stratum": 1, "poll": 1024, "precision": 7.45058e-09, "root-delay": 0, "root-dispersion": 0, "ref-id": "XFUN", "ref-ts": 3961497821.676918507, "result": [ { "origin-ts": 3961498121.667407990, "receive-ts": 3961498121.676918507, "transmit-ts": 3961498121.676956654, "final-ts": 3961498121.687090874, "rtt": 0.019645, "offset": 0.000312 } ] } -- Marco