3Com S7906E - Switch, Configuration Manual

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1-8
A single device can have a maximum of 128 associations at the same time, including static associations
and dynamic associations. A static association refers to an association that a user has manually
created by using an NTP command, while a dynamic association is a temporary association created by
the system during operation. A dynamic association will be removed if the system fails to receive
messages from it over a specific long time. In the client/server mode, for example, when you carry out a
command to synchronize the time to a server, the system will create a static association, and the server
will just respond passively upon the receipt of a message, rather than creating an association (static or
dynamic). In the symmetric mode, static associations will be created at the symmetric-active peer side,
and dynamic associations will be created at the symmetric-passive peer side; in the broadcast or
multicast mode, static associations will be created at the server side, and dynamic associations will be
created at the client side.
Configuring NTP Client/Server Mode
For devices working in the client/server mode, you only need to make configurations on the clients, but
not on the servers.
Follow these steps to configure an NTP client:
To do… Use the command… Remarks
Enter system view system-view —
Specify an NTP server for the
device
ntp-service unicast-server
[ vpn-instance
vpn-instance-name ]
{ ip-address | server-name }
[ authentication-keyid keyid |
priority | source-interface
interface-type interface-number
| version number ] *
Required
No NTP server is specified by
default.
z
In the ntp-service unicast-server command, ip-address must be a unicast address, rather than a
broadcast address, a multicast address or the IP address of the local clock.
z
When the source interface for NTP messages is specified by the source-interface argument, the
source IP address of the NTP messages will be configured as the primary IP address of the
specified interface.
z
A device can act as a server to synchronize the clock of other devices only after its clock has been
synchronized. If the clock of a server has a stratum level higher than or equal to that of a client’s
clock, the client will not synchronize its clock to the server’s.
z
You can configure multiple servers by repeating the ntp-service unicast-server command. The
clients will choose the optimal reference source.