This guide describes the complete integration of Didactum monitoring devices into Nagios (Nagios Core and Nagios XI). The objective is the centralized monitoring of all connected sensors - temperature, humidity, leakage, voltage, door contacts, and others - via the Nagios monitoring system using SNMP.

Nagios monitors the Didactum device via the SNMP protocol (Simple Network Management Protocol). 

Nagios queries specific OIDs (Object Identifiers) from the device at configurable intervals and evaluates the returned values against defined thresholds.

Monitoring process

1. The Nagios scheduler triggers a check (e.g. every 5 minutes).
2. The Nagios plugin check_snmp sends an SNMP query to the Didactum device (UDP port 161).
3. The Didactum device responds with the current sensor value.
4. The plugin compares the value with the configured warning and critical thresholds.
5. Nagios sets the service status to OK, WARNING, CRITICAL or UNKNOWN.
6. On status changes, notifications (email, SMS, ticket) are triggered.

Nagios service states

• Nagios Core 4.x or Nagios XI (current version) with administrator access
• Nagios server: Linux (Debian/Ubuntu or RHEL/CentOS)
• Packages nagios-plugins and snmp installed on the Nagios server
• Didactum monitoring device reachable on the network, SNMP enabled
• Network communication: UDP port 161 from the Nagios server to the Didactum device allowed
• SNMP community string known (default: public)
• Optional: Didactum MIB file for readable OID names

Example network configuration

3.1 Enable SNMP

1. Open the Didactum web interface: [http://192.168.1.100](http://192.168.1.100), log in with the admin account.
2. Navigation: Settings → Network → SNMP (or: Settings → Network → SNMP).
3. Set the following parameters:
   • SNMP enabled: Yes
   • SNMP version: v2c (recommended) or v3
   • Community string: public (change in production)
   • SNMP port: 161
   • Allowed Managers: enter the IP of the Nagios server (192.168.1.20)
4. Save the settings.

Attention: Change the default community string public in production environments. Use the same string later in all Nagios check commands.

3.2 Test reachability from the Nagios server

# SNMP walk – list all available OIDs:
snmpwalk -v2c -c public 192.168.1.100 1.3.6.1.4.1.3854
 
# Query a single value (temperature sensor 1):
snmpget -v2c -c public 192.168.1.100 1.3.6.1.4.1.3854.1.2.2.1.16.1.3.1
 
# Query system description (basic test):
snmpget -v2c -c public 192.168.1.100 1.3.6.1.2.1.1.1.0

4.1 Install required packages

# Debian / Ubuntu:
sudo apt update
sudo apt install nagios-plugins nagios-plugins-extra snmp snmpd snmp-mibs-downloader -y
 
# RHEL / CentOS / Rocky Linux:
sudo dnf install nagios-plugins-all net-snmp net-snmp-utils -y

4.2 Test the check_snmp plugin

# Call the plugin directly (path may vary depending on distribution):
/usr/lib/nagios/plugins/check_snmp \
  -H 192.168.1.100 \
  -C public \
  -o 1.3.6.1.4.1.3854.1.2.2.1.16.1.3.1 \
  -w 300 -c 350 \
  --label="Temperature S1"

Expected output at 23.5°C (raw value 235):

OK - Temperature S1: 235 | Temperature S1=235;300;350

4.3 Integrate Didactum MIB file (optional)

# Copy the MIB file to the SNMP MIB directory:
sudo cp DIDACTUM-RACKMONI2-MIB.mib /usr/share/snmp/mibs/
 
# Enable MIBs in /etc/snmp/snmp.conf:
echo "mibs +DIDACTUM-RACKMONI2-MIB" | sudo tee -a /etc/snmp/snmp.conf
 
# Test using MIB name instead of OID number:
snmpget -v2c -c public -m +DIDACTUM-RACKMONI2-MIB 192.168.1.100 tempValue.1

Note:

• The name of the .mib file (check on the Didactum device) may vary

5.1 Create configuration file

Create a new configuration file for the Didactum device:

sudo nano /etc/nagios/conf.d/didactum.cfg

5.2 Host definition

define host {
    use                     generic-host
    host_name               didactum-rack01
    alias                   Didactum Rack Monitoring Unit – Server room A
    address                 192.168.1.100
    check_command           check-host-alive
    max_check_attempts      3
    check_interval          5
    retry_interval          1
    check_period            24x7
    notification_interval   60
    notification_period     24x7
    notifications_enabled   1
    contact_groups          admins
    notes                   Didactum Rack Monitoring Unit II – SNMP v2c
    icon_image              server.png
    statusmap_image         server.gd2
}

5.3 Host group for all Didactum devices

define hostgroup {
    hostgroup_name          didactum-devices
    alias                   Didactum monitoring devices
    members                 didactum-rack01, didactum-rack02
}

6.1 Command definition for SNMP checks

First define a reusable check command. Insert it into /etc/nagios/conf.d/didactum.cfg or commands.cfg:

# General SNMP check command:
define command {
    command_name    check_snmp_didactum
    command_line    $USER1$/check_snmp \\
                    -H $HOSTADDRESS$ \\
                    -C $ARG1$ \\
                    -o $ARG2$ \\
                    -w $ARG3$ \\
                    -c $ARG4$ \\
                    $ARG5$
}
 
# SNMP check with factor (for temperature × 10):
define command {
    command_name    check_snmp_didactum_factor
    command_line    $USER1$/check_snmp \\
                    -H $HOSTADDRESS$ \\
                    -C $ARG1$ \\
                    -o $ARG2$ \\
                    -w $ARG3$ \\
                    -c $ARG4$ \\
                    --label="$ARG5$" \\
                    -u "$ARG6$"
}
 
# SNMP status check (0 = OK, everything else = problem):
define command {
    command_name    check_snmp_status
    command_line    $USER1$/check_snmp \\
                    -H $HOSTADDRESS$ \\
                    -C $ARG1$ \\
                    -o $ARG2$ \\
                    -w 0:0 \\
                    -c 1:
}}

Note: 

$USER1$ is typically /usr/lib/nagios/plugins – check /etc/nagios/resource.cfg or adjust it.

6.2 Monitor temperature sensors

Didactum returns temperature values with a factor of 10 (235 = 23.5°C). 

Therefore the warning/critical values in the checks must also be specified × 10:

# Temperature sensor 1 (warning at 30 °C, critical at 35 °C):
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Temperature Sensor 1 – Rack Front
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.16.1.3.1!300!350!--label="Temp S1 (×10)"
    check_interval          5
    retry_interval          1
    max_check_attempts      3
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
    notes                   Raw value × 10 – value 300 = 30 °C, 350 = 35 °C
}
 
# Temperature sensor 2 – rack rear:
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Temperature Sensor 2 – Rack Rear
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.16.1.3.2!300!350!--label="Temp S2 (×10)"
    check_interval          5
    retry_interval          1
    max_check_attempts      3
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
}
 
# Temperature status sensor 1 (0=OK, 1=warn, 2=alarm):
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Temperature Status Sensor 1
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.16.1.4.1
    check_interval          2
    retry_interval          1
    max_check_attempts      2
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
}

6.3 Monitor leak sensors

Leak status: value 0 = no water, value 1 = leak detected. Immediate alerting without a warning stage is recommended:

# Leak sensor 1 – immediate alert at value > 0:
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Leak Sensor 1 – Floor Area
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.18.1.4.1
    check_interval          1
    retry_interval          1
    max_check_attempts      1
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
    notes                   0 = dry, 1 = leak detected – IMMEDIATE ALERT
    first_notification_delay  0
}
 
# Leak sensor 2:
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Leak Sensor 2 – Cable Duct
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.18.1.4.2
    check_interval          1
    retry_interval          1
    max_check_attempts      1
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
}

6.4 Monitor humidity sensors

# Humidity sensor 1 (warning 70 %, critical 80 %):
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Humidity Sensor 1
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.17.1.3.1!20:70!10:80!--label="Humidity S1" -u "%rF"
    check_interval          5
    retry_interval          1
    max_check_attempts      3
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
    notes                   Range: 20–80 % rF (ASHRAE recommendation)
}

6.5 Monitor voltage sensors

Voltage is also delivered with a factor of 10 (2298 = 229.8 V):

# Voltage sensor 1 (warning outside 207–253 V, critical outside 196–260 V):
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Voltage Sensor 1 – PDU Input
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.15.1.3.1!2070:2530!1960:2600!--label="Voltage S1 (×10)"
    check_interval          5
    retry_interval          1
    max_check_attempts      3
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
    notes                   Raw value × 10 – EN 50160: 207–253 V (±10 %)
}

6.6 Monitor door contacts and other sensors

# Door contact sensor 1 (0=closed, 1=open):
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Rack door contact front
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.10.1.3.1
    check_interval          1
    retry_interval          1
    max_check_attempts      1
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
    notes                   0 = closed (OK), 1 = open (CRITICAL)
}
 
# Smoke detector sensor 1:
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Smoke Detector Sensor 1
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.14.1.3.1
    check_interval          1
    retry_interval          1
    max_check_attempts      1
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
}
 
# System uptime:
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Didactum System Uptime
    check_command           check_snmp_didactum!public!1.3.6.1.2.1.1.3.0!0:!0:!--label="Uptime"
    check_interval          60
    retry_interval          5
    max_check_attempts      3
    check_period            24x7
    notification_period     24x7
    contact_groups          admins
}

6.7 Service group for all Didactum checks

define servicegroup {
    servicegroup_name       didactum-sensors
    alias                   Didactum sensor monitoring
    members                 didactum-rack01,Temperature Sensor 1 – Rack Front, \\
                            didactum-rack01,Temperature Sensor 2 – Rack Rear, \\
                            didactum-rack01,Leak Sensor 1 – Floor Area, \\
                            didactum-rack01,Humidity Sensor 1, \\
                            didactum-rack01,Voltage Sensor 1 – PDU Input
}

All OIDs are based on the Didactum Enterprise OID base 1.3.6.1.4.1.3854. The placeholder {n} stands for the sensor index (1 = first sensor, etc.).

7.1 Temperature sensors

7.2 Leak sensors

7.3 Humidity sensors

7.4 Additional sensors

7.5 Nagios threshold format (quick reference)

In addition to active polling, Nagios can also receive passive SNMP traps from the Didactum device. 

In that case, the device sends a trap immediately when an event occurs (e.g. leak detected) — without waiting for the next polling cycle.

8.1 Install and configure snmptrapd

# Debian / Ubuntu:
sudo apt install snmptrapd -y
 
# Open the configuration file:
sudo nano /etc/snmp/snmptrapd.conf

Enter the following:

# Community string for incoming traps:
authCommunity log,execute,net public
 
# Trap handler for Didactum traps:
traphandle 1.3.6.1.4.1.3854 /usr/local/bin/didactum_trap_handler.sh
 
# Logging:
doNotLogTraps no
outputOption fq

8.2 Enable snmptrapd

# Enable and start the service:
sudo systemctl enable snmptrapd
sudo systemctl start snmptrapd
 
# Check status:
sudo systemctl status snmptrapd

8.3 Nagios passive check results via NSCA

Traps can be forwarded to Nagios via NSCA (Nagios Service Check Acceptor) as passive check results:

# Install NSCA:
sudo apt install nsca -y
 
# Create the trap handler script:
sudo nano /usr/local/bin/didactum_trap_handler.sh

#!/bin/bash
# Didactum SNMP trap handler for Nagios
# Receives trap data and forwards it as passive checks
 
NAGIOS_HOST="didactum-rack01"
NSCA_HOST="127.0.0.1"
NSCA_PORT="5667"
SEND_NSCA="/usr/sbin/send_nsca"
 
# Read trap OID and value from snmptrapd input:
TRAP_OID="$1"
TRAP_VALUE="$2"
 
# Leak trap:
if echo "$TRAP_OID" | grep -q "1.3.6.1.4.1.3854.1.7.2"; then
    echo "$NAGIOS_HOST\\tLeak Sensor 1 – Floor Area\\t2\\tCRITICAL: Leak detected!" \\
    | $SEND_NSCA -H $NSCA_HOST -p $NSCA_PORT
fi
 
# Temperature alarm trap:
if echo "$TRAP_OID" | grep -q "1.3.6.1.4.1.3854.1.7.1"; then
    echo "$NAGIOS_HOST\\tTemperature Sensor 1 – Rack Front\\t2\\tCRITICAL: Temperature alarm triggered!" \\
    | $SEND_NSCA -H $NSCA_HOST -p $NSCA_PORT
fi

sudo chmod +x /usr/local/bin/didactum_trap_handler.sh

8.4 Important Didactum trap OIDs

On the Didactum device: 

Enter the trap receiver IP as the Nagios server IP, port 162 (UDP), under Settings → Network → SNMP → Trap Receiver.

9.1 Contact definition

define contact {
    contact_name                    it-admin
    alias                           IT administrator
    use                             generic-contact
    email                           [admin@example.com](mailto:admin@example.com)
    pager                           +4915112345678
    service_notification_period     24x7
    host_notification_period        24x7
    service_notification_options    w,u,c,r
    host_notification_options       d,u,r
    service_notification_commands   notify-service-by-email
    host_notification_commands      notify-host-by-email
}

9.2 Contact group

define contactgroup {
    contactgroup_name       admins
    alias                   IT administrators
    members                 it-admin
}

9.3 Recommended notification settings for leak detection

# For leak services: immediate notification, no delay:
define service {
    use                         generic-service
    host_name                   didactum-rack01
    service_description         Leak Sensor 1 – Floor Area
    check_command               check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.18.1.4.1
    check_interval              1
    max_check_attempts          1
    first_notification_delay    0
    notification_interval       5
    notification_period         24x7
    contact_groups              admins
}

9.4 Recommended thresholds

# Check Nagios configuration for errors:
sudo nagios -v /etc/nagios/nagios.cfg
 
# Reload Nagios service (after configuration changes):
sudo systemctl reload nagios
 
# Test SNMP reachability:
snmpwalk -v2c -c public 192.168.1.100 1.3.6.1.4.1.3854
 
# Query a single OID value:
snmpget -v2c -c public 192.168.1.100 1.3.6.1.4.1.3854.1.2.2.1.16.1.3.1
 
# Test check_snmp plugin directly:
/usr/lib/nagios/plugins/check_snmp \\
  -H 192.168.1.100 -C public \\
  -o 1.3.6.1.4.1.3854.1.2.2.1.16.1.3.1 \\
  -w 300 -c 350
 
# Monitor Nagios log in real time:
sudo tail -f /var/log/nagios/nagios.log
 
# Check snmptrapd log:
sudo journalctl -u snmptrapd -f
 
# Open firewall port for SNMP (ufw):
sudo ufw allow 161/udp
sudo ufw allow 162/udp

Ready-to-use configuration file as a starting template for a Didactum host with the most important sensors:

################################################################################
# Didactum Monitoring Integration – Nagios Configuration
# File: /etc/nagios/conf.d/didactum.cfg
# Adjust: IP address, community string, number of sensors
################################################################################
 
# ── HOST ──────────────────────────────────────────────────────────────────────
define host {
    use                     generic-host
    host_name               didactum-rack01
    alias                   Didactum Rack Monitoring – Server Room A
    address                 192.168.1.100
    check_command           check-host-alive
    max_check_attempts      3
    check_interval          5
    notification_period     24x7
    contact_groups          admins
}
 
# ── COMMANDS ──────────────────────────────────────────────────────────────────
define command {
    command_name    check_snmp_didactum
    command_line    $USER1$/check_snmp -H $HOSTADDRESS$ -C $ARG1$ -o $ARG2$ -w $ARG3$ -c $ARG4$ $ARG5$
}
 
define command {
    command_name    check_snmp_status
    command_line    $USER1$/check_snmp -H $HOSTADDRESS$ -C $ARG1$ -o $ARG2$ -w 0:0 -c 1:
}
 
# ── SERVICES ──────────────────────────────────────────────────────────────────
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Temperature Sensor 1 – Rack Front
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.16.1.3.1!300!350!
    check_interval          5
    max_check_attempts      3
    contact_groups          admins
}
 
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Temperature Sensor 2 – Rack Rear
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.16.1.3.2!300!350!
    check_interval          5
    max_check_attempts      3
    contact_groups          admins
}
 
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Leak Sensor 1 – Floor Area
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.18.1.4.1
    check_interval          1
    max_check_attempts      1
    first_notification_delay  0
    contact_groups          admins
}
 
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Humidity Sensor 1
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.17.1.3.1!20:70!10:80!
    check_interval          5
    max_check_attempts      3
    contact_groups          admins
}
 
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Voltage Sensor 1 – PDU Input
    check_command           check_snmp_didactum!public!1.3.6.1.4.1.3854.1.2.2.1.15.1.3.1!2070:2530!1960:2600!
    check_interval          5
    max_check_attempts      3
    contact_groups          admins
}
 
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Door Contact Rack Door Front
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.10.1.3.1
    check_interval          1
    max_check_attempts      1
    contact_groups          admins
}
 
define service {
    use                     generic-service
    host_name               didactum-rack01
    service_description     Smoke Detector Sensor 1
    check_command           check_snmp_status!public!1.3.6.1.4.1.3854.1.2.2.1.14.1.3.1
    check_interval          1
    max_check_attempts      1
    contact_groups          admins
}

For firmware-specific OIDs and supported sensor types, always consult the current Didactum device documentation.