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Supported device types and versions

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SNMP protocol protocol (Simple Network Management Protocol) is used for monitoring and administration of network components. It allows the detection of the network devices' status and the changing of their settings. In an application, it is possible to monitor the functionality of e.g., routers, switches, computers, etc.

To create a station equipped with the SNMP protocol, it is necessary to have a UDP line (line of of TCP/IP-UDP type). It is worth mentioning here that a TCP/IP-UDP line line in the perception of the D2000 system is actually a UDP socket, which is a logical device to support communication of individual stations. It is not possible to use stations with a different protocol on a line where stations with the SNMP protocol exist!

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Communication line configuration

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• Communication line category: TCP/IP-UDP.
• UDP parameters:
  • Host: There are three ways:
    1. The IP address of the particular network interface – datagrams will be transmitted and received only via this interface.
       Example:  192.168.1.10
    2. The symbolic name of a particular network interface.
       Example:  D2SRV_PRIMARY
    3. ALL -the configured UDP port is opened on all available network interfaces. An optimal network interface should be used for communication based on routing tables. The reception of messages will be performed on all network interfaces.
  • Port: UDP port number (0 through 65535) from which the D2000 KOM process sends requests and receives the responses. If the value is 0, the port number is assigned automatically by the OS.
    Note: Ports 161 and 162 are the standard UDP ports used in SNMP, but they are often reserved for SNMP agents - that is why it is recommended to choose different ports. Problems can occur with value 0 (zero) if the network uses firewalls and other security measures. Then, a specific port needs to be configured on the firewalls so that the packets from this port are passed via through the firewalls.

Note:
If SNMP protocol needs to run in a redundant system, where two instances of the D2000 KOM process are running concurrently on two different computers and the IP address cannot be positively determined in the line configuration, it is appropriate to choose „ALL“ configuration option or to name the network addresses identically as e.g. SNMP_LAN and assign them a correct IP address in the hosts file of each computer. See example:

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• Communication protocol: SNMP Manager.
• Station's address: it is defined in the format IP_address1[:port1], IP_address2[:port2].

IP_address may be set in decimal dotted notation (e.g. 192.168.0.1) or as a name (e.g. SrvMoxa1), which assumes address translation by means of DNS or a hosts file. Address1 and Address2 concern the existence of primary and backup lines/routes. Address 2 is usable, for example, for a server containing two network interface cards, which is connected to two different network segments available via two different network paths.

Port is a number in the range 1..65535 on which an SNMP agent expects communication to take place. As the default (if not statedconfigured, or set to 0) port, the standard port 161 will be used.

Note:

• If the line has only a primary IP address configured (numerical or symbolic), UDP packets are sent from this address to both IP addresses of the station. One numerical primary IP address of the line + two IP addresses of the station are valid for a network topology where the local network is non-redundant, but the remote network (where the station is located) is accessible via two redundant communication paths.
• If the line has both IP addresses configured, UDP packets to IP_address1 leave from the primary IP address of the line, and UDP packets to IP_address2 leave from the backup IP address of the line.
  The situation when, e.g., IP_address1 is not configured conforms to the topology when the station is connected to a backup communication path only.

Protocol
The employed version of the SNMP protocol – one of the options can be selected:

• SNMP_V1 – the oldest version – does not support any secured access to the SNMP agent. It only distinguishes the objects that are freely accessible (public) and those belonging to a restricted group (private).
• SNMP_V2 – a version that supports authentication to access individual data types - an agent might (not) provide a particular set of data for an anonymous user (a manager,...) and different data for a user whose identity has been verified by entering a correct name and password.
• SNMP_V2C – the same as SNMP_V2 – the D2000 system does not distinguish these variants.
• SNMP_V3 – so far the latest protocol version – besides functions provided by SNMP_V2C, supports functions for authentication and encryption. It requires entering the name of an authentication server and authentication keys , to authenticate prior to communication with an agent, and keys for encrypting communication.

SNMP_V2, SNMP_V2C, and SNMP_V3 are not supported yet. Neither the writing into the SNMP agent nor reading MIB branches as a table (structured I/O tags or directly entered structure entries) are is supported.

Station protocol parameters

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Address1: Address of I/O tag. The address specifies the OID (Object identifier) of an object. It is displayed in a numerical format, e.g., 1.3.6.1.2.1.1.1.0. The address can also start with a dot, which is ignored, unless the Address Root parameter is set (e.g., .1.3.6.1.2.1.1.1.0),

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If it would be necessary to have information on whether the primary or backup IP address of the device is available, it is possible to use the so-called forced addressing by selecting the option Only Primary, respectively Only secondary. This will ensure that the I/O tag value will be acquired only from the primary, respectively, secondarystation address. The Both option is the standard option, where the values of the I/O tags are obtained continuously from both addresses of the station (if they are configured). The Passive option means that the value of the I/O tag is not read directly, but is obtained indirectly as a copy of the value of another I/O tag with the same address, but in the active mode, e.g., Only primary.

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