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Further notes on operation
8.7 SNMP agent
As default, time-of-day synchronization is not activated for the CP and it does not therefore
forward the time. However, the internal clock of the CP is synchronized in this case, if a time-
of-day frame is received from the K bus or from Industrial Ethernet.
Synchronization using one of the two modes described here must be configured in STEP 7
in the properties dialog of the CP - "Time-of-Day Synchronization" tab.
For more detailed information on the parameters and options, refer to the online help in the
properties dialog.
Coordinating forwarding of the time of day with several CPs
If there is more than one CP in a station connected to the same network, only one of these
CPs is allowed to pass on time-of-day messages.
You can therefore made the following settings in the configuration:
● Automatic
● From station to LAN
● From LAN to station
8.7
SNMP agent
SNMP (Simple Network Management Protocol)
The CP supports data queries via SNMP in Version 1. It returns the contents of certain MIB
objects according to the MIB II standard, LLDP MIB and Automation System MIB.
SNMP is a protocol for managing networks. To transmit data, SNMP uses the
connectionless UDP protocol.
The information on the properties of SNMP-compliant devices is entered in MIB files (MIB =
Management Information Base).
Where to find further information
For more detailed information on working with MIB files, refer to the documentation of the
SNMP client you are using (example of an SNMP client: SNMP OPC Server from SIMATIC
NET).
You will find more information on MIB on the following SIMATIC NET Internet page:
Link to MIBs: (http://support.automation.siemens.com/WW/view/en/15177711)
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The CP receives the time-of-day message from the LAN or from the station and forwards
it to the station or to the LAN.
If several CPUs are being operated in the station, this automatic setting can lead to
collisions. To avoid this, you can specify the direction of forwarding with the following
options:
CP 343-1 ERPC
Manual, 03/2010, C79000-G8976-C239-02
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