HP 5500 Ei 5500 Si Switch Series Configuration Guide

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NTP message format 
NTP uses two types of messages: clock synchronization and NTP control messages. All NTP messages 
mentioned in this document refer to NTP clock sy nchronization messages. NTP control messages are 
used in environments where network management is needed. Because NTP control messages are not 
essential for clock synchronization, they are not described in this document. 
A clock synchronization message is encapsulated in a UDP message in the format shown in  Figure 6. 
Figure 6...

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•  Stratum —An 8-bit integer that indicates the stratum level of the local clock, with the value ranging 
from 1 to 16. Clock precision decreases from stratum 1 through stratum 16. A stratum 1 clock has 
the highest precision, and a stratum 16 clock is not synchronized. 
•   Po l l—An 8-bit signed integer that indicates the ma ximum interval between successive messages, 
which is called the poll interval. 
•   Precision —An 8-bit signed integer that indicates the precision of the local clock. 
•...

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In client/server mode, a client can synchronize to a server, but a server cannot synchronize to a client. 
Symmetric peers mode 
Figure 8 Symmetric peers mode 
 
 
In symmetric peers mode, devices that operate in symmetric active mode and symmetric passive mode 
exchange NTP messages with the Mode field 3 (client mode) and 4 (server mode). Then the device that 
operates in symmetric active mode periodically se nds clock synchronization messages, with the Mode 
field in the messages set to 1...

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Multicast mode 
Figure 10 Multicast mode 
 
 
In 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. When a client receives the first multicast message, the client and the server start to 
exchange messages with the Mode field...

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Configuring the client/server mode 
For devices operating in client/server mode, make configurations on the clients. 
If you specify the source interface for NTP messages by specifying the source interface source-interface 
option, NTP uses the primary IP address of the specified interface as the source IP address of the NTP 
messages. 
A device can act as a server to synchronize other devices only after it is synchronized. If a server has a 
stratum level higher than or equal to a client, the...

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Step Command Remarks 
2.  Specify a symmetric-passive 
peer for the device.  ntp-service
 unicast-peer 
[ vpn-instance  vpn-instance-name  ] 
{  ip-address |  peer-name } 
[ authentication-keyid  keyid  | 
priority  | source-interface 
interface-type interface-number  | 
version  number ] *  By default, no symmetric-passive 
peer is specified. 
Only the HP 5500 EI supports the 
vpn-instance
 keyword. 
The  ip-address  argument must be a 
unicast address, rather than a 
broadcast address, a multicast...

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Step Command Remarks 
1.  Enter system view. 
system-view  N/A 
2.  Enter Layer 3 Ethernet 
interface view or VLAN 
interface view.   interface
 interface-type 
interface-number   This command enters the view of 
the interface for sending NTP 
broadcast messages. 
You can configure an Ethernet port 
as a Layer 3 Ethernet port only on 
the HP 5500 EI switch. 
3.
  Configure the device to 
operate in NTP broadcast 
server mode.  ntp-service
 broadcast-server  
[ authentication-keyid  keyid  | 
version...

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Step Command Remarks 
3.  Configure the device to 
operate in NTP multicast 
server mode.  ntp-service
 multicast-server  
[ ip-address ] 
[ authentication-keyid  keyid  | ttl 
ttl-number  | version  number  ] *  A multicast server can synchronize 
broadcast clients only when its 
clock has been synchronized. 
 
Configuring optional parameters 
This section explains how to configure the optional parameters of NTP. 
Specifying the source interface for NTP messages 
If you specify the source interface...

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Step Command Remarks 
2.  Enter Layer 3 Ethernet 
interface view or VLAN 
interface view.  interface
 interface-type 
interface-number   You can configure an Ethernet port 
as a Layer 3 Ethernet port only on 
the HP 5500 EI switch. 
3.
  Disable the interface from 
receiving NTP messages.  ntp-service in-interface disable  By default, an interface is enabled 
to receive NTP messages. 
 
Configuring the allowed maximum number of dynamic 
sessions 
A single device can have a maximum of 128 associatio...

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•  query —Control query permitted. This level of righ t permits the peer devices to perform control 
query to the NTP service on the local device, but it  does not permit a peer device to synchronize to 
the local device. Control query refers to the query of some states of the NTP service, including 
alarm information, authentication status, and clock source information. 
•   synchronization —Server access only. This level of right permits a peer device to synchronize to the 
local device, but it...