SNMP

SNMP can be used in two ways: to obtain some basic statistics of the status of the Allegro Network Multimeter or to get informed about incidents via SNMP traps.

Query information via SNMP

SNMP support can be enabled in the menu Settings → Remote access & export → SNMP.

Configuration settings

Configuration value	Available options	Firmware Version
Enabled	off on for SNMPv1 support	< 3.0
SNMP service	disabled SNMPv1 SNMPv2c SNMPv3	>= 3.0
Community	The community string used by SNMPv1/v2c. Default value or empty is public.
User name	The SNMPv3 user name.	>= 3.0 (moved into user settings with 4.2)
User password	The SNMPv3 password for authentication and encryption.	>= 3.0 (moved into user settings with 4.2)
Authentication method	SHA SHA-256 SHA-512	<= 3.0 (moved into user settings with 4.2)
Encryption method	AES	>= 3.0 (moved into user settings with 4.2)
Name	Translates to sysName.	>= 4.2
Location	Translates to sysLocation.	>= 4.2
Contact	Translates to sysContact.	>= 4.2
Multiple User (SNMPv3)	Multiple users with: - username - password - authentication method (see above) and authentication password - encoding method (see above) and encoding password Authentication and encoding password are now different settings, both have to be set.	>= 4.2

Supported attributes

• hostname (1.3.6.1.2.1.1.5.0)
• uptime (1.3.6.1.2.1.25.1.1.0)
• interfaces (1.3.6.1.2.1.2.1.0, 1.3.6.1.2.1.3.0, 1.3.6.1.2.1.4.0)
• temperature (1.3.6.1.4.1.2021.13.16.2.1.2.1 -.7)
• ICMP (1.3.6.1.2.1.5)
• storage (1.3.6.1.2.1.25.2.3.1.3)

Supported transport methods

The SNMP access uses UDP on port 161. If SNMPv3 is enabled, it uses the User-Based Security Model (USM) for authentication and encryption. In this mode, only authPriv is supported.

Available SNMP versions and transport layer

SNMP version	Protocol and port	Security
v1/v2c	UDP 161	none
v3	UDP 161	USM authPriv

Available feature combinations for SNMP access

Feature set	SNMP v1	SNMP v3
plain access	yes	no
authentication	no	mandatory (SHA, SHA-256, SHA-512)
encryption	no	mandatory (AES)
USM	no	yes
via TLS	no	no
via DTLS	no	no
via SSH	no	no

SNMP trap

The Allegro Network Multimeter can be configured to use SNMP traps as incident channel.

Testing reception and proper decoding of SNMP traps

Sending SNMP traps may be tricky for several reasons. Since SNMP traps are sent as UDP packets, the sender does not get informed of successful transfer. Furthermore, the settings of the sender and receiver must match, so that the trap will be accepted and can be decoded. Finally, the trap receiver should be able to process the Management Information Base (MIB) to interpret the sent attributes.

A reference installation is described here to test basic SNMP trap transfer and processing.

SNMP V3 traps

Trap receiver setup

The setup uses a Docker image of Debian stable.

• Create and start a container with exposed UDP ports 161 and 162:

  docker run -it --name "snmp_trap_receiver_test" -p 161:161/udp -p 162:162/udp debian:stable

• Some of the required packages are in the non-free repository, so edit /etc/apt/sources.list to contain the following entries:

  deb http://deb.debian.org/debian stable main non-free
  deb http://deb.debian.org/debian-security stable-security main non-free
  deb http://deb.debian.org/debian stable-updates main non-free

• Install the following packages:

  apt-get update
  apt-get install snmp-mibs-downloader snmptrapd

• From outside the container, copy the MIB file into the Docker container:

  docker cp ALLEGRO-NETWORK-MULTIMETER-MIB.txt
  snmp_trap_receiver_test:/usr/share/snmp/mibs/

• Configure access control in /etc/snmp/snmptrapd.conf:

  #
  # EXAMPLE-trap.conf:
  # An example configuration file for configuring the Net-SNMP snmptrapd agent.
  #
  ###############################################################################
  #
  # This file is intended to only be an example.
  # When the snmptrapd agent starts up, this is where it will look for it.
  #
  # All lines beginning with a '#' are comments and are intended for you
  # to read. All other lines are configuration commands for the agent.
  #
  # PLEASE: read the snmptrapd.conf(5) manual page as well!
  #
  #authCommunity log,execute,net private
  #authCommunity log,execute,net public
  #
  ## send mail when get any events
  #traphandle default /usr/bin/traptoemail -s smtp.example.org foobar@example.org
  #
  ## send mail when get linkDown
  #traphandle .1.3.6.1.6.3.1.1.5.3 /usr/bin/traptoemail -s smtp.example.org foobar@example.org
  
  ## user definition to test snmptrapd:
  createUser -e 0x8000000001020304 homeoffice SHA "foobarfoo" AES "foobarbaz"
  authUser log,execute,net homeoffice

• Start listening for incoming SNMP traps:

  /usr/sbin/snmptrapd -A -Le -p /run/snmptrapd.pid -f -d -m ALLEGRO-NETWORK-MULTIMETER-MIB

Allegro Network Multimeter configuration

Configure an SNMP trap incident channel in the Allegro Network Multimeter:

• Navigate to: Generic → Incidents
• Select tab: Notification channels
• Click Add channel:
  • Select Type: SNMP trap
  • SNMP trap settings:
    • Version: SNMPv3
    • Trap receiver hostname/IP: <the host of your Docker container running Debian with snmptrapd>
    • Authentication protocol: SHA
    • Authentication password: foobarfoo
    • Privacy protocol: AES
    • Privacy password: foobarbaz
    • Security name: homeoffice
    • Security level: authPriv
    • Engine ID: 0x8000000001020304

Configure an incident rule in the Allegro Network Multimeter, which uses the configured channel:

• Select tab: Incident rules
• Trigger an incident, it will be decoded and shown in the Docker container.