Discussion

Engine boots, the ntpdate utility runs early in the boot process, before chassisd and
rpd are up. The only thing that is up and configured at that point is fxp0.
With this method of setting up NTP, the router gets the time once, when it boots,
and sets its clock based on the time it receives from the server. While you could
choose this as the only method for getting accurate time on the router, the clock time
can drift over long periods, so it is a better idea to get the time when the router boots
and to also synchronize the time periodically with time servers to slowly correct any
drifting.
If the NTP boot server is another router, you cannot boot both routers at once, for
instance, if you are power-cycling all the routers in your POP. You must start the
boot server first.
See Also
Recipe 6.4
6.4 Synchronizing Time Periodically
Problem
You want to periodically resynchronize the time on the router to limit the effects of
clock drift.
Solution
Configure the router to periodically get time updates from an NTP server:
[edit system]
aviva@router1# set ntp server 192.168.27.46
aviva@router1# show
system {
ntp {
server 192.168.27.46;
}
}
Discussion
Setting the router’s time by configuring a boot server provides a one-time method for
the router to get time when it boots. However, once a router is up and stable, you
will almost never have to reboot it, so if its time starts to drift from the time on your
other network devices, you have to go into the router and manually reconfigure the
time. To automatically keep the router in sync with the rest of the network, you can
have it periodically get time updates from an NTP server. To do this, place the
JUNOS NTP software into NTP server mode with the set ntp server command,
specifying the IP address of the NTP server. The NTP server will then periodically
send the correct time to the router, which then adjusts its system clock.
Synchronizing Time Periodically | 185
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