Industrial Ethernet Security with CP 1543-1
14.3 NTP client
Communication
Function Manual, 11/2019, A5E03735815-AH
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14.3 NTP client
Functionality
To check the time validity of a certificate and the time stamp of log entries, the date and time
are maintained on the CP 1543-1 as on the CPU. This time can be synchronized with NTP.
The CP 1543-1 forwards the synchronized time to the CPU via the backplane bus of the
automation system. This way the CPU also receives a synchronized time for the time events
in program execution.
The automatic setting and periodic synchronization of the time takes place either via a
secure or non-secure NTP server. You can assign a maximum of 4 NTP servers to the
CP 1543-1. A mixed configuration of non-secure and secure NTP servers is not possible.
14.4 SNMP
Functionality
Like the CPU, the CP 1543-1 supports the transfer of management information using the
Simple Network Management Protocol (SNMP). To achieve this, an "SNMP agent" is
installed on the CP/CPU that receives and responds to the SNMP queries. Information about
the properties of devices capable of SNMP is contained in so-called MIB files (Management
Information Base) for which the user needs to have the appropriate rights.
With SNMPv1, the "community string" is also sent. The "community string" is like a password
that is sent along with the SNMP query. The requested information is sent when the
"community string" is correct. The request is discarded when the string is incorrect.
With SNMPv3, data can be transferred encrypted. To do this, select either an authentication
method or an authentication and encryption method.
Possible selection:
● Authentication algorithm: none, MD5, SHA-1
● Encryption algorithm: none, AES-128, DES
You can deactivate the use of SNMP for the CP/CPU. Deactivate SNMP if the security
guidelines in your network do not permit SNMP or if you use your own SNMP solution.
To find out how to deactivate SNMP for the CPU, refer to section Disabling SNMP
(Page 57).
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