Another 11.1-RELEASE install minor annoyance (ntpd)
g8kbvdave at googlemail.com
Thu Oct 12 12:45:16 UTC 2017
On 12/10/17 13:00, freebsd-questions-request at freebsd.org wrote:
> All your Linksys needs for NTP support is to allow UDP to any, port 123.
> And the response packets, obviously.
Usually, that will be the normal default NAT router behaviour, incoming
packets from a requested site (as signified by previous outgoing packets
to the same site) will pass back into the LAN unmolested and be directed
to the requesting local IP address.
Unless you or someone else has intentionally blocked NTP traffic at your
border. (I've yet to find even an ISP supplied box that has NTP
blocked, as a "user".)
About the only time (pun unintended) you need to poke a hole in a
border/gateway/firewall, is if you want to run a publicly accessible NTP
(or any other) server. Then, you do need to poke a hole (usually port
123 for NTP) so the great unwashed web can reach into your shiny new
In such cases, it's also wise to keep all the NTPD baggage up to date.
I'm not aware of any current issues, but in the not too distant past
"there have been some issues that were exploited for DDoS atacks!"
(I don't know. Is it possible to jail a NTP server?)
I take it you know about the NTP pool project? Not suggesting you join
it (unless you wish to) but as an external resource for a LAN based
machine to sync to, it is a superbly reliable resource. Virtually
guaranteed to be a better source of time than your ISP's servers (that
here in the UK seem to reside on already very busy border/gateway machines.)
If you have an unreliable or a throttled internet service. There is the
option of using a GPS receiver that also has a PPS signal output, so
your local NTP server stays accurate, even if it can't reach out to
other NTP servers..
http://www.satsignal.eu/ntp/FreeBSD-GPS-PPS.htm (Old in respect to
FreeBSD, but the principles are sound.)
But we're getting well into "Time Nuts" territory in that case.
It was the need for an accurate and more importantly "stable" local time
source (that didn't drift +- some seconds during the day, due to my own
ISP "messing things about") that I learnt about FreeBSD in the first place.
Regards to All.
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