H3C S7500E Series Ethernet Switches Operation Manual

Operation Manual – NTP
H3C S7500E Series Ethernet Switches Chapter 1 NTP Configuration
1-7
the network delay between client and the server. Then, the client enters the broadcast
client mode and continues listening to broadcast messages, and synchronizes its local
clock based on the received broadcast messages.
IV. Multicast mode
Network
Client
Server
After receiving the first
multicast message the client
sends a request
Clock synchronization message
exchange (Mode 3 and Mode 4)
Periodically multicasts clock
synchronization messages (Mode 5)
Calculates the network delay
between client and server and
enters the multicast client mode
Periodically multicasts clock
synchronization messages (Mode 5)
Receives multicast messages
and synchronizes its local
clock
，
Figure 1-6 Multicast mode
In the multicast mode, a server periodically sends clock synchronization messages to
the user-configured multicast address, or, if no multicast address is configured, to the
default NTP multicast address 224.0.1.1, with the Mode field in the messages set to 5
(multicast mode). Clients listen to the multicast messages from servers. After a client
receives the first multicast message, the client and the server start to exchange
messages, with the Mode field set to 3 (client mode) and 4 (server mode) to calculate
the network delay 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.
1.1.5 Multiple Instances of NTP
 Note:
Support for this feature varies with devices.
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 NTP, as long as they are in the same VPN. The specific functions are as
follows:
z The NTP client on a customer edge device (CE) can be synchronized to the NTP
server on another CE.