3Com Switch 4210 9-Port, Configuration Manual

Page: 375 / 567

Configuring NTP Implementation Modes 373
Configuring the NTP
Symmetric Peer Mode
For switches working in the symmetric peer mode, you need to specify a
symmetric-passive peer on the symmetric-active peer.
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In the symmetric peer mode, you need to execute the related NTP
configuration commands (refer to “Configuring NTP Implementation Modes”
for details) to enable NTP on a symmetric-passive peer; otherwise, the
symmetric-passive peer will not process NTP messages from the
symmetric-active peer.
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The remote device specified by remote-ip or peer-name serves as the peer of
the local Ethernet switch, and the local switch works in the symmetric-active
mode. In this case, the clock of the local switch and that of the remote device
can be synchronized to each other.
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remote-ip must not be a broadcast address, a multicast address or the IP
address of the local clock.
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After you specify an interface for sending NTP messages through the
source-interface keyword, the source IP address of the NTP message will be
configured as the IP address of the specified interface.
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Typically, the clock of at least one of the symmetric-active and
symmetric-passive peers should be synchronized first; otherwise the clock
synchronization will not proceed.
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You can configure multiple symmetric-passive peers for the local switch by
repeating the
ntp-service unicast-peer command. The clock of the peer with
the smallest stratum will be chosen to synchronize with the local clock of the
switch.
Configuring NTP
Broadcast Mode
For switches working in the broadcast mode, you need to configure both the
server and clients. The broadcast server periodically sends NTP broadcast messages
to the broadcast address 255.255.255.255. The switches working in the NTP
broadcast client mode will respond to the NTP messages, so as to start the clock
synchronization.
A 3Com Switch 4210 can operate as a broadcast server or a broadcast client.
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Refer to Table 285 for configuring a switch to work in the NTP broadcast server
mode.
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Refer to Table 286 for configuring a switch to work in the NTP broadcast client
mode.
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A broadcast server can synchronize broadcast clients only after its clock has been
synchronized.
Table 284 Configure a symmetric-active switch
Operation Command Description
Enter system view system-view -
Specify a symmetric-passive
peer for the switch ntp-service unicast-peer {
remote-ip | peer-name } [
authentication-keyid key-id
| priority | source-interface
Vlan-interface vlan-id |
version number ]*
Required
By default, a switch is not
configured to work in the
symmetric mode.