H3C Technologies H3C S7500E Series Switches - Manual (Page 72)

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z The NTP client on a PE can be synchronized to the NTP server on another PE through a
designated VPN instance.
z The NTP server on a PE can synchronize the NTP clients on multiple CEs in different
VPNs.
z 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.
z A PE is a device directly connecting to CEs. In an MPLS network, all events related to VPN
processing occur on the PE.
NTP Configuration Task List
Complete the following tasks to configure NTP:
Task Remarks
Configuring the Operation Modes of NTP Required
Configuring the Local Clock as a Reference Source Optional
Configuring Optional Parameters of NTP Optional
Configuring Access-Control Rights Optional
Configuring NTP Authentication Optional
Configuring the Operation Modes of NTP
Devices can implement clock synchronization in one of the following modes:
z Client/server mode
z Symmetric mode
z Broadcast mode
z Multicast mode
For the client/server mode or symmetric 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.