Hello Dimitar On 06.01.2014 18:25, Dimitar Vassilev wrote:
1. Is it really necessary ppsX and gpsX devices to match the serial port sequence Example cuau1 (COM1) to be linked to gps1 device or you can have gps0 device I've linked cuau1 to both gps0 and gps1. However as I read it matters what is the last digit 127.127.20.0 will use gps0 and 127.127.20.1 will use gps1. Am I right?
The mapping does not matter, you just need the right 127.127.20.x depending on the used device ID. I have a Garmin GPS 18x LVC running on FreeBSD 9.1 at the serial port cuau5 with the following settings in /etc/devfs.conf:
# for the Garmin GPS 18x LVC / ntpd link cuau5 gps1 link cuau5 pps1
2. Should I put flag 2 as redundant e.g fudge 127.127.20.0 flag1 1 flag2 0 flag3 1 time2 0.600 or should I leave it as fudge 127.127.20.0 flag1 1 flag3 1 time2 0.600
And the following settings for it in my /etc/ntp.conf: # Garmin GPS 18x LVC # flag3 controls the kernel PPS discipline: 0 for disable # (default), 1 for enable. # needs kernel 'options PPS_SYNC' or modul pps server 127.127.20.1 prefer mode 1 minpoll 4 maxpoll 4 fudge 127.127.20.1 time1 0.000 flag3 0 refid GPS server 127.127.22.1 mode 1 minpoll 4 maxpoll 4 fudge 127.127.22.1 time1 0.000 flag3 1 refid PPS The ntpq -p output shows this: remote refid st t when poll reach delay offset jitter ================================================================== +GPS_NMEA(1) .GPS. 0 l 3 16 377 0.000 0.001 0.000 oPPS(1) .PPS. 0 l 14 16 377 0.000 0.001 0.000
I have put the default restrictions as per https://support.ntp.org/bin/view/Support/AccessRestrictions both for IPv4 and v6 - restrict default kod nomodify notrap nopeer noquery
I have the following lines (do not forget to add the 'limited'): # by default, don't trust and don't allow modifications # see -> https://support.ntp.org/bugs/show_bug.cgi?id=320 # should be fixed with ntp-4.2.5p178 (or later), eg. -4 / -6 not # needed any more restrict -4 default limited kod notrap nomodify nopeer noquery restrict -6 default limited kod notrap nomodify nopeer noquery restrict default limited kod notrap nomodify nopeer noquery
3. When syncing time with peers should I pick stratum-1 as I will be running stratum-1 eventually myself or pick a stratum-2 or 3?
Stratum 2 or 3 are also fine. Your ntpd just needs some other ntp servers to compare if the local GPS gives good time or not. If all the other servers have the same offset, then it will drop the GPS to invalid.
4. Is it needed to announce myself as stratum-1 or this is to be determined from the stats in the system?
This depends if your ntpd has synced and prefers the local GPS then it will announce itself as Straturm 1 (as the local GPS is Stratum 0). If it is in sync with one of the other ntp servers, then it will announce itself depending on the other servers Stratum with the one from there plus 1. E.g. if in sync with a Stratum 2, the local ntpd will announce itself as Stratum 3.
I'm aware that there will be quite interest in my small box anyway no matter which stratum it is.
If synced to the GPS it will be Stratum 1, which it should be, unless you have bad GPS reception.
5. Should I care for anything else?
It looks quite good so far. If you are running e.g. ipfw or other firewall on the host, it would probably be a good idea to have the following rules set very early, so the ntp packets do not need to go through all the other rules:
allow udp from any to me 123 in allow udp from me 123 to any out bye Fabian _______________________________________________ pool mailing list [email protected] http://lists.ntp.org/listinfo/pool
