L-IP User Manual
144
LOYTEC
Version 6.1
LOYTEC electronics GmbH
As SNMP has several restrictions on what can be represented, the following mappings are
made:
Binary data points
. Binary data points are mapped to the INTEGER type. FALSE
is mapped to 0, TRUE is mapped to 1 and an invalid value is mapped to -1.
Analog data points
: SNMP has no standard way to represent floating point
values, so their values are mapped to the STRING type. A value of “--“ identifies
an invalid value
Multistate data points
: Multistate data points are mapped to the STRING data
type. Their values are represented by the multi-state text labels.
SNMP variable names have to be unique within their MIB, so data points with the same
name in different folders are made unique by the following name scheme:
dpNNNNXUUUUUUUU
, e.g.
dpFreeMemoryX00000003
. NNNN is the data point name with all
forbidden characters removed (only a-z, A-Z and 0-9 is allowed). UUUUUUUU is replaced
with the unique ID of the data point.
Figure 139: Downloading device-specific MIB files
Figure 139 shows the Web UI page which allows downloading the device specific MIB file.
The “Download MIB file” buttons generates a MIB file which can be used by a network
management tool. The “Download XML file” button generates an XML-encoded
representation of the MIB contents.
Note that the MIB files are dependent on the data point configuration, so that changes in the
data point configuration will change the MIB contents.
10.1.4 SNMP Security
As SNMP provides access to internal device information which could be exploited for an
attack, SNMP should be used only in internal, non-critical environments.
SNMP Version 2C uses unencrypted authentication and payload. The community string is
transmitted in clear text and can be easily extracted from captured network traffic.
SNMP Version 3 supports encrypted authentication and payload encryption. LOYTEC
devices support only authentication. The password is not transmitted in clear text then.
LOYTEC devices do not support write accesses via SNMP.