3Com Switch 8800 Advanced Software V5 Configuration Guide

1068 CHAPTER 85: NTP CONFIGURATION
Multiple Instances of
NTP
The server/client mode and symmetric mode support multiple instances of NTP
and thus support clock synchronization within an MPLS VPN network. Namely,
network devices (CEs and PEs) at different physical location can get their clocks
synchronized through MPLS VPN connection, as long as they are in the same VPN.
The specific functions are as follows:
■ The NTP client on a customer edge device (CE) can be synchronized to the NTP
server on another CE.
■ The NTP client on a CE can be synchronized to the NTP server on a provider
edge device (PE).
■ The NTP client on a PE can be synchronized to the NTP server on a CE through
a designated VPN instance.
■ The NTP server on a PE can synchronize multiple NTP clients on different CEs.
n
■ A CE is a device that has an interface directly connecting to the service provider
(SP). A CE is not "aware of" the presence of the VPN.
■ A PE is a device that directly connecting to CEs. In an MPLS network, all events
related to VPN processing occur on the PE.
NTP Configuration
Task List
Complete these tasks to configure NTP:
Configuring the
Operation Modes of
NTP
According to the devices’ position in the network and the network structure,
devices can implement clock synchronization in one of the following modes:
■ Server/client mode
■ Symmetric peers mode
■ Broadcast mode
■ Multicast mode
For the server/client mode or symmetric peers mode, you need to configure only
clients or symmetric-active peers; for the broadcast or multicast mode, you need
to configure both servers and clients.
n
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
Configuration tasks Remarks
“Configuring the Operation Modes of NTP”
on page 1068
Required
“Configuring the Local Clock as a Reference
Source” on page 1072
Optional
“Configuring Optional Parameters of NTP” on
page 1072
Optional
“Configuring Access-Control Rights” on page
1073
Optional
“Configuring NTP Authentication” on page
1074
Optional