Symmetricom ND-CLK User Manual page 23

address ranges for multicasting are defined and governed by RFC3171, IANA IPv4 Multicast
Guidelines.
Typically, the multicast address range 224.0.1.0 - 224.0.1.255 (224.0.1/24) [ Internetwork
Control Block] is utilized for NTP traffic, however, please refer to the
application and implementation.
[Note: While listening to NTP broadcasts/multicasts, the network clock cannot be configured to
query the time server.]
[Note: Some NTP/SNTP clients will expect NTP servers to operate on port 123 and cannot be
configured to utilize alternate ports.]
The network clock can be configured to either listen to NTP multicast or broadcasts
only, or to query the NTP time server at a selected interval. The default
configuration is to query the NTP server at 10-minute intervals. To configure the
network clock device to only listen to NTP broadcasts, click the checkbox for
"Listen for NTP broadcasts only", and enter a "Broadcast timeout" in minutes. The
default timeout is 60 minutes.
Display Control
The lower half of the window configures the face of the network clock. Options in
this configuration region may be grayed out; this indicates invalid or unavailable
options for this model of network clock.
Time Zone Settings
The Time Zone button included in the right half of the window, gives the clock
complete flexibility to display any time zone. First select the time zone, by clicking
the Time Zone button. This opens a new window that gives you a list of time zones,
including descriptions to help with the selection. Select the Time Zone and click OK
to close the window. Changes are not applied until you click OK or the Apply button
on the main Configuration window.
ND-CLK User Manual- Rev 1.0.1 - Sep-08
RFC3171
20
for your specific
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