H3C S5500-EI series Operation Manual page 1157

Operation Manual – NTP
H3C S5500-EI Series Ethernet Switches
receiving the message, the servers automatically work in the server mode and send a
reply, with the Mode field in the messages set to 4 (server mode). Upon receiving the
replies from the servers, the client performs clock filtering and selection, and
synchronizes its local clock to that of the optimal reference source.
In this mode, a client can be synchronized to a server, but not vice versa.
II. Symmetric peers mode
Figure 1-4 Symmetric peers mode
A switch working in the symmetric active mode periodically sends clock synchronization
messages, with the Mode field in the message set to 1 (symmetric active); the switch
that receives this message automatically enters the symmetric passive mode and
sends a reply, with the Mode field in the message set to 2 (symmetric passive). By
exchanging messages, the symmetric peers mode is established between the two
switches. Then, the two switches can synchronize, or be synchronized by, each other. If
the clocks of both switches have been already synchronized, the switch whose local
clock has a lower stratum level will synchronize the clock of the other switch.
III. Broadcast mode
Figure 1-5 Broadcast mode
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Chapter 1 NTP Configuration