HP VPN Firewall Appliances System Management and Maintenance Configuration Guide

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The following describes how an association is established in different operation modes:
• Client/server mode—After you specify an NTP server, the system creates a static association on the
client. The server simply responds passively upon the receipt of a message, rather than creating an
association (static or dynamic).
• Symmetric active/passive mode—After you specify a symmetric-passive peer on a symmetric active
peer, static associations are created on the symmetric-active peer, and dynamic associations are
created on the symmetric-passive peer.
• Broadcast or multicast mode—Static associations are created on the server, and dynamic
associations are created on the client.
A single device can have a maximum of 128 concurrent associations, including static associations and
dynamic associations.
To configure the allowed maximum number of dynamic sessions:
Ste
p
Command Remarks
1. Enter system view.
system-view N/A
2. Configure the maximum number of
dynamic sessions allowed to be
established locally.
ntp-service max-dynamic-sessions
number
The default is 100.
Configuring access-control rights
From the highest to lowest, the NTP service access-control rights are peer, server, synchronization, and
query. If a device receives an NTP request, it performs an access-control right match and uses the first
matched right. If no matched right is found, the device drops the NTP request.
• Query—Control query permitted. This level of right permits the peer devices to perform control
query to the NTP service on the local device but does not permit a peer device to synchronize its
clock to that of the local device. The so-called "control query" refers to query of some states of the
NTP service, including alarm information, authentication status, clock source information, and so
on.
• Synchronization—Server access only. This level of right permits a peer device to synchronize its
clock to that of the local device but does not permit the peer devices to perform control query.
• Server—Server access and query permitted. This level of right permits the peer devices to perform
synchronization and control query to the local device but does not permit the local device to
synchronize its clock to that of a peer device.
• Peer—Full access. This level of right permits the peer devices to perform synchronization and control
query to the local device and also permits the local device to synchronize its clock to that of a peer
device.
The access-control right mechanism provides only a minimum level of security protection for a system
running NTP. A more secure method is identity authentication.
Configuration prerequisites
Before you configure the NTP service access-control right to the local device, create and configure an
ACL associated with the access-control right. For more information about ACLs, see Access Control
Configuration Guide.