3Com 4210 PWR - Configuring NTP Implementation Modes

372 CHAPTER 35: NTP CONFIGURATION
Configuring NTP
Implementation
Modes
A Switch 4210 can work in one of the following NTP modes:
■ “Configuring NTP Server/Client Mode”
■ “Configuring the NTP Symmetric Peer Mode”
■ “Configuring NTP Broadcast Mode”
■ “Configuring NTP Multicast Mode”
n
To protect unused sockets against attacks by malicious users and improve security,
the 3Com Switch 4210 Family provides the following functions:
■ UDP port 123 is opened only when the NTP feature is enabled.
■ UDP port 123 is closed as the NTP feature is disabled.
These functions are implemented as follows:
■ 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.
n
■ 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.
Tabl e 283 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.