Thanks, that's very helpful.
Here's what I see:
S Name/IP Address Auth COpts EOpts Last Score Interval Leap
=======================================================================
* 1PPS N -P--- -P--- 1 1.0 -7ns +31ns N
D foobar N -P--- -P--- 3 1.0 -1550ns +2091ns N
Going through the man pages, "foobar" is in "D" state when its root distance (in a recent measurement) is greater than combinelimit * root distance of current best source's root distance. So, I tried increasing combinelimit to a higher value and it started combining.
The 1PPS signal is coming from a time server appliance that has a good clock and uses a GNSS ref clock as well; "foobar" is another good source in the same site. In such a case, is it best to combine both 1PPS and "foobar" sources; or should I just use 1PPS (if available) and fallback to other sources if 1PPS isn't available (that is, don't forcefully combine them)?
Also, one thing that I noticed is that if I stop the 1PPS signals, it's not falling back to "foobar"; 1PPS remains as the best source. Should I add something in the configs to make this work?
S Name/IP Address Auth COpts EOpts Last Score Interval Leap
=======================================================================
* 1PPS N ----- ----- 228 1.0 -200us +200us N
D foobar N ----- ----- 1 1.0 -2650ns +1040ns N
Thanks in advance,
Abhijith