Mobatime NMI, Монтаж и инструкция по эксплуатации, Страница: 12 / 24

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7.6 SNMP
For the integration into a monitoring system, the NMI supports SNMP notifications
(traps) (SNMP version 2c). As an SNMP agent, the NMI can send alarm and alive traps
to an SNMP manager in the network (e.g. network management tool HP OpenView or
similar). For this purpose, the IP address of the SNMP manager must be configured
(with DHCP or PC tool MOBA-NMS). The trap structures are defined in an MIB file (for
details, see document BE-800793). Alarm traps are used to inform the SNMP manager
about errors. Alive traps are sent periodically and signal the availability and the status
of the device to the SNMP managers. The interval of the alive traps can be set with the
PC tool MOBA-NMS.
7.7 Local time calculation
The NMI is synchronized to UTC (coordinated world time). In order to calculate and
display the local time, the NMI requires additional information in the shape of a time
zone entry. The NMI can save 1 time zone entry which can be edited over the network
using the PC tool MOBA-NMS.
The local time setting can only be configured using MOBA-NMS.
Alternatively, the calculation of the local time based on the time zone entry of a time
zone server is supported. In the unicast mode, it requests the entry from the configured
NTP server. In the multicast mode, it receives the corresponding entry on the config-
ured group address.
7.8 Accuracy / Loss of synchronization
The deviation in the synchronized state is usually s/-50 ms.
The NMI signals a loss of synchronization after 24 hours through putting out the 12
o’clock command. The deviation after 24 h without synchronization is typically smaller
+/-2 s (quartz accuracy: 20 ppm at room temperature).
Notice:
The mentioned deviations depend on the accuracy and performance of
the time source (NTP server). The NTP reception can be influenced by
the network load and devices (hub, switch, router, firewall, etc.).
7.9 Redundant time source
The availability of NTP servers as time source can be improved through a redundant
operation in the network. Depending on the operation mode of the NMI, the following
strategy is provided (also works for time zone servers):
7.9.1 NTP client unicast
As a DHCP option or through manual configuration (MOBA-NMS), up to four different
NTP server addresses can be announced to the interface. If three time requests in a
row are not answered by the current server, the interface switches to the next server (if
available). The duration until the change is dictated by the set request interval (default:
3 x 10 seconds). After a restart of the interface, the request begins at the first server.
7.9.2 NTP client multicast
Two servers which send NTP packages from the same group address (multicast IP)
are to be installed. The sending intervals of the two servers have to be set so that the
primary server is the synchronization source in normal operation. The synchronization