3Com 4500 PWR 26-Port Configuration Manual page 651

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.
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.
Follow these steps to configure an NTP client:
To do...
Enter system view
Configure an NTP client
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.
remote-ip cannot be a broadcast address, a multicast address or the IP address of the local clock.
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.
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.
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.
Follow these steps to configure a symmetric-active switch:
To do...
Enter system view
Use the command...
system-view
ntp-service unicast-server { remote-ip |
server-name } [ authentication-keyid key-id |
priority | source-interface Vlan-interface
vlan-id | version number ]*
Use the command...
system-view
54-7
Remarks
—
Required
By default, the
switch is not
configured to work
in the NTP client
mode.
Remarks
—