1-6
z
UDP port 123 is opened only when the NTP feature is enabled.
z
UDP port 123 is closed as the NTP feature is disabled.
These functions are implemented as follows:
z
Execution of one of the
ntp-service unicast-server
,
ntp-service unicast-peer
,
ntp-service
broadcast-client
,
ntp-service broadcast-server
,
ntp-service multicast-client
, and
ntp-service
multicast-server
commands enables the NTP feature and opens UDP port 123 at the same time.
z
Execution of the
undo
form of one of the above six commands disables all implementation modes
of the NTP feature and closes UDP port 123 at the same time.
Configuring NTP Server/Client Mode
For switches working in the server/client mode, you only need to perform configurations on the clients,
and not on the servers.
Table 1-3
Configure an NTP client
Operation
Command
Description
Enter system view
system-view
—
Configure an NTP
client
ntp-service
unicast-server
{
remote-ip
|
server-name
} [
authentication-keyid
key-id
|
priority
|
source-interface
Vlan-interface
vlan-id
|
version
number
]*
Required
By default, the switch
is not configured to
work in the NTP client
mode.
z
The remote server specified by
remote-ip
or
server-name
serves as the NTP server, and the local
switch serves as the NTP client. The clock of the NTP client will be synchronized by but will not
synchronize that of the NTP server.
z
remote-ip
cannot be a broadcast address, a multicast address or the IP address of the local clock.
z
After you specify an interface for sending NTP messages through the
source-interface
keyword,
the source IP address of the NTP message will be configured as the primary IP address of the
specified interface.
z
A switch can act as a server to synchronize the clock of other switches only after its clock has been
synchronized. If the clock of a server has a stratum level lower 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
client will choose the optimal reference source.
Configuring the NTP Symmetric Peer Mode
For switches working in the symmetric peer mode, you need to specify a symmetric-passive peer on the
symmetric-active peer.