H3C Technologies H3C SR8800 - Manual (Page 69)

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between client and the server. Then, the client enters the multicast client mode and continues listening to
multicast messages, and synchronizes its local clock based on the received multicast messages.
NOTE:
In symmetric peers mode, broadcast mode and multicast mode, the client (or the symmetric active peer)
and the server (the symmetric passive peer) can work in the specified NTP working mode only after they
exchange NTP messages with the Mode field being 3 (client mode) and the Mode field being 4 (server
mode). During this message exchange process, NTP clock synchronization can be implemented.
NTP-supported MPLS L3VPN
When operating in client/server mode or symmetric mode, NTP supports MPLS L3VPN, and thus realizes
clock synchronization within an MPLS VPN network. In other words, network devices (CEs and PEs) at
different physical location can get their clocks synchronized through NTP, 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.
• The NTP client on a PE can be synchronized to the NTP server on another PE through a designated
VPN.
• The NTP server on a PE can synchronize the NTP clients on multiple CEs in different VPNs.
NOTE:
•
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:
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
Routers can implement clock synchronization in one of the following modes:
• Client/server mode