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358
C
12: F
S
HAPTER
ILE
NTP Configuration
Configuring NTP
Operating Mode
M
YSTEM
ANAGEMENT
Switch A sends an NTP packet to Switch B. The packet carries the timestamp
■
10:00:00am (T
When the NTP packet arrives at Switch B, Switch B adds a local timestamp
■
11:00:01am (T
When the NTP packet leaves Switch B, Switch B adds another local timestamp
■
11:00:02am (T
When Switch A receives the acknowledgement packet, it adds a new
■
timestamp 10:00:03am (T
Now Switch A collects enough information to calculate the following two
important parameters:
The delay for a round trip of an NTP packet traveling between the Switch A and
■
B: Delay= (T
Offset of Switch A clock relative to Switch B clock: offset= ( (T
■
In this way, Switch A uses the above information to set the local clock and
synchronize it with the clock on Switch B.
The operating principle of NTP is briefly introduced above. For more information,
refer to RFC1305.
NTP is used for time synchronization throughout a network. NTP configuration
tasks include:
Configure NTP operating mode
■
Configure NTP ID authentication
■
Set NTP authentication key
■
Set the specified key to be reliable
■
Set a local interface for transmitting NTP packets
■
Set an external reference clock or the local clock as the master NTP clock
■
Enable/Disable an interface to receive NTP packets
■
Set control authority to access the local Switch service
■
Set maximum local sessions
■
You can set the NTP operating mode of a Switch according to its location in the
network and the network structure. For example, you can set a remote server as
the time server of the local equipment. In this case the local Switch works as an
NTP client. If you set a remote server as a peer of the local Switch, the local
equipment operates in symmetric active mode. If you configure an interface on
the local Switch to transmit NTP broadcast packets, the local Switch will operate in
broadcast mode. If you configure an interface on the local Switch to receive NTP
broadcast packets, the local Switch will operate in broadcast client mode. If you
configure an interface on the local Switch to transmit NTP multicast packets, the
local Switch will operate in multicast mode. Or you may also configure an interface
on the local Switch to receive NTP multicast packets, the local Switch will operate
in multicast client mode.
) that tells when it left Switch A.
1
) to it.
2
) to it.
3
) to it.
4
-T
) - (T
-T
).
4
1
3
2
-T
) + (T
-T
) ) /2.
2
1
4
3
- Quick Links:
- Configuration Guide
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