HP VPN Firewall Appliances System Management and Maintenance Configuration Guide

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Configuring optional parameters for NTP
This section explains how to configure the optional parameters of NTP.
Specifying the source interface for NTP messages
If you specify the source interface for NTP messages, the device sets the source IP address of the NTP
messages as the primary IP address of the specified interface when sending the NTP messages. NTP
packets might not be received because of state changes of an interface on the device. To avoid that
problem, specify the loopback interface as the source interface.
When the device responds to an NTP request received, the source IP address of the NTP response is
always the destination IP address of the NTP request.
Follow these guidelines when you specify the source interface for NTP messages:
• The source interface for NTP unicast messages is the interface specified in the ntp-service
unicast-server or ntp-service unicast-peer command.
• The source interface for NTP broadcast or multicast messages is the interface where you configure
the ntp-service broadcast-server or ntp-service multicast-server command.
To specify the source interface for NTP messages:
Ste
p
Command Remarks
1. Enter system view.
system-view
N/A
2. Specify the source interface
for NTP messages.
ntp-service source-interface
interface-type interface-number
By default, no source interface is
specified for NTP messages, and
the system uses the IP address of
the interface determined by the
matching route as the source IP
address of NTP messages.
Disabling an interface from receiving NTP messages
If NTP is enabled, NTP messages can be received from all the interfaces by default, and you can disable
an interface from receiving NTP messages through the following configuration.
To disable an interface from receiving NTP messages:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Enter interface view.
interface interface-type
interface-number
N/A
3. Disable the interface from
receiving NTP messages.
ntp-service in-interface disable
By default, an interface is enabled
to receive NTP messages.
Configuring the allowed maximum number of dynamic sessions
NTP has the following types of associations:
• Static association—A manually created association.
• Dynamic association—Temporary association created by the system during NTP operation. A
dynamic association is removed if no messages are exchanged over a specific period of time.