EOE-W55RP20 SNMP Module SNMP Setup Guide

Firmware 1.2.0

This guide covers installing the SNMP tools on the manager PC, reading and writing over SNMPv3, v1/v2c communities, where objects are placed in the OID tree, CSV mapping, and Traps and Informs.

Wiring and IP setup are covered in the Getting Started Guide. If you are new to the module, first do chapter 0, Installing the SNMP manager, then complete up to step 4 of the Getting Started Guide, and continue here from chapter 1.

Chapter	Contents
Chapter 0	Installing the SNMP manager (net-snmp)
Chapter 1	Reading and writing with SNMPv3
Chapter 2	Turning on SNMPv1 and v2c
Chapter 3	Object addresses (OID)
Chapter 4	Registering many objects at once with a CSV file
Chapter 5	Confirmed SET
Chapter 6	Sending Traps and Informs
Chapter 7	Troubleshooting

The examples use the module address 192.168.0.100, the manager PC 192.168.0.20 and net-snmp as the manager tool. In the diagrams, items marked ▶ are introduced in that section; the others were explained earlier. All command arguments and responses are described in the AT Command Guide.

0. Installing the SNMP manager

The SNMP manager is the program that reads (GET) and writes (SET) the module's values and receives the notifications (Traps) the module sends. The examples in this guide use net-snmp, a free set of command-line tools.

Program	What it does
`snmpget` · `snmpwalk` · `snmpset`	Read and write the module's values
`snmptrapd`	Receive the Traps and Informs the module sends (used in chapter 6)

net-snmp 5.8 or later is required. The module uses SHA-256 for SNMPv3 authentication, which older versions of net-snmp do not support. Always check the version after installing.

Linux

Ubuntu · Debian:

sudo apt update

sudo apt install snmp snmptrapd

Fedora · RHEL · Rocky:

sudo dnf install net-snmp-utils net-snmp

Windows

The net-snmp installer published for Windows is an older version that does not support SHA-256. On Windows, use WSL (a Windows feature that runs Ubuntu inside Windows).

Open PowerShell as administrator and install Ubuntu. Restart the PC when it finishes.
```
wsl --install -d Ubuntu
```
Open Ubuntu from the Start menu and set the user name and password it asks for on the first run.
From here on, the procedure is the same as on Linux. In the Ubuntu window, enter the Ubuntu · Debian commands from Linux above to install net-snmp.
```
sudo apt update
```
```
sudo apt install snmp snmptrapd
```
Then do Checking the installation and When results show only numbers below in the Ubuntu window, exactly as on Linux.

When using WSL, enter all the commands in this guide, such as snmpget · snmpwalk · snmpset · snmptrapd, in the Ubuntu window, not in Windows PowerShell or Command Prompt. Commands that read and write values (snmpget · snmpwalk · snmpset) work without any extra setup.

Receiving Traps in WSL needs one more setting. By default WSL uses an internal address that differs from the PC's, so a Trap the module sends to the PC's address does not reach snmptrapd inside WSL. On Windows 11, create a .wslconfig file in your user folder (C:\Users\<name>) with the two lines below, run wsl --shutdown in PowerShell, and open Ubuntu again.
[wsl2]
networkingMode=mirrored
Then allow incoming UDP port 162 in Windows Firewall.

macOS

Install with Homebrew. The net-snmp that comes with macOS is an older version, so add the newly installed one to the front of PATH.

brew install net-snmp

echo 'export PATH="$(brew --prefix net-snmp)/bin:$(brew --prefix net-snmp)/sbin:$PATH"' >> ~/.zshrc

source ~/.zshrc

Checking the installation

snmpget --version

NET-SNMP version: 5.9.4.pre2

Any version from 5.8 on is fine. You can now follow step 4 of the Getting Started Guide to read the module's sysDescr.

When results show only numbers

With the default settings on Ubuntu · Debian, responses show numbers instead of names.

iso.3.6.1.2.1.1.1.0 = STRING: "EOE-ioNIC_SNMP SNMPv3 module, firmware 1.2.0"

Communication is working; only the display differs. To see names such as SNMPv2-MIB::sysDescr.0, install the standard MIB files and comment out the mibs : line in /etc/snmp/snmp.conf by adding # in front of it.

sudo apt install snmp-mibs-downloader

sudo sed -i 's/^mibs :/# mibs :/' /etc/snmp/snmp.conf

snmp-mibs-downloader is in the multiverse repository on Ubuntu and non-free on Debian. If you cannot install it, you can keep the numeric display; it works the same.

Using a graphical tool

A graphical tool such as a MIB browser can be used instead of the command line. First check that it supports SNMPv3 SHA-256 authentication and AES-128 encryption. If it does not, create a separate SHA-1 user on the module (AT Command Guide chapter 6).

1. Reading and writing with SNMPv3

This chapter uses the user admin1 created in step 4 of the Getting Started Guide. How to create more users or choose roles and security levels is in AT Command Guide chapter 6.

Set net-snmp's -l option according to the security level chosen on the module.

Module (`AT+USMADD`)	net-snmp `-l`
`NOAUTHNOPRIV`	`noAuthNoPriv`
`AUTHNOPRIV`	`authNoPriv`
`AUTHPRIV`	`authPriv`

Read all the standard objects at once.

snmpwalk -v3 -l authPriv -u admin1 -a SHA-256 -A authpass123 -x AES -X privpass123 \
         192.168.0.100 1.3.6.1.2.1.1

The 11 standard objects below can be read from the start, without creating any objects. All of them are read-only.

OID	Name
`1.3.6.1.2.1.1.1.0` ~ `1.3.6.1.2.1.1.7.0`	sysDescr · sysObjectID · sysUpTime · sysContact · sysName · sysLocation · sysServices
`1.3.6.1.2.1.11.1.0` · `.2.0` · `.3.0` · `.6.0`	snmpInPkts · snmpOutPkts · snmpInBadVersions · snmpInASNParseErrs

If you get Invalid authentication protocol, your net-snmp version is too old to support SHA-256. Upgrade net-snmp to 5.8 or later (chapter 0), or create the user with SHA1.

Writing a value requires a writable (RW) object. The standard objects are all read-only, so create a test object writeTest as number 3 on the AT port.

AT+OBJADD=3,"writeTest",Integer32,RW,VOLATILE

AT+SAVE

The address of writeTest is 1.3.6.1.4.1.52942.3.0 (chapter 3). Write a value to it from the manager.

snmpset  -v3 -l authPriv -u admin1 -a SHA-256 -A authpass123 -x AES -X privpass123 \
         192.168.0.100 1.3.6.1.4.1.52942.3.0 i 1

The write succeeded if you see this:

SNMPv2-SMI::enterprises.52942.3.0 = INTEGER: 1

At the same time, the host MCU receives a notification on the AT port that the value changed.

 +SNMPSET:3,1
          : :
          : :
          : '-  new value the manager wrote
          '---  number of the object that changed

A SET to an object that does not exist returns a noCreation error. Objects cannot be created over SNMP, only with AT commands or a CSV file (chapter 4).

2. Turning on SNMPv1 and v2c

v1 and v2c are off by default. Both rely on a community string alone for access control, and the string is sent over the network unencrypted. Turn them on only when necessary, and only on a trusted network.

Communities are shared by v1 and v2c, so register them once in 2.1. Then follow 2.2 (v2c) or 2.3 (v1), depending on the version your manager uses.

2.1 Registering communities

A community is a password-like string that a v1 · v2c manager sends with each request, and the role assigned to it determines what it may do. Create one for reading and one for writing.

AT+COMMADD="ro-poll",MONITOR

AT+COMMADD="rw-ctrl",OPERATOR

AT+SAVE

Check with this command:

AT+COMM?

The result should look like this:

+COMM:"ro-poll",Monitor,ENABLED
+COMM:"rw-ctrl",Operator,ENABLED

On the web interface, the same settings are on the v1/v2c tab.
The rules for communities are in AT Command Guide chapter 6.

Communities are not accepted until their version is turned on, which the next sections do.

A wrong setting gets no response at all. Requests in a disabled version or with a wrong community do not even get an error response, so the manager only shows Timeout. If nothing answers, check AT+SNMPVER? and AT+COMM? first.

2.2 Reading and writing with v2c

Turn on v2c. AT+SNMPVER takes all the versions to answer, so include v3, which you are already using. Leaving v3 out disables SNMPv3 access.

AT+SNMPVER=2,3

AT+SAVE

Check with this command:

AT+SNMPVER?

The result should look like this:

+SNMPVER:2,3

Read values from the manager PC. -v2c selects the version and -c the community.

snmpget  -v2c -c ro-poll 192.168.0.100 1.3.6.1.2.1.1.5.0

snmpwalk -v2c -c ro-poll 192.168.0.100 1.3.6.1.4.1.52942

Write to writeTest (object 3), created in chapter 1, using the rw-ctrl community, which has write permission.

snmpset  -v2c -c rw-ctrl 192.168.0.100 1.3.6.1.4.1.52942.3.0 i 1

2.3 Reading and writing with v1

v1 is the first version of SNMP. Turn it on when your management system supports only v1. Add 1 to the version list; if you do not need v2c, 1,3 is enough.

AT+SNMPVER=1,2,3

AT+SAVE

Check with this command:

AT+SNMPVER?

The result should look like this:

+SNMPVER:1,2,3

On the manager PC, select the version with -v1. Use the communities created in 2.1.

snmpget  -v1 -c ro-poll 192.168.0.100 1.3.6.1.2.1.1.5.0

snmpwalk -v1 -c ro-poll 192.168.0.100 1.3.6.1.4.1.52942

snmpset  -v1 -c rw-ctrl 192.168.0.100 1.3.6.1.4.1.52942.3.0 i 1

v1 lacks the features added in v2c and later, so the same objects give slightly different results.

What differs with v1	Why
`Counter64` objects are missing from a walk, and `snmpget` returns `noSuchName`	v1 has no 64-bit counter type. The object still exists; it just cannot be read over v1
`snmpbulkwalk` cannot be used	GETBULK, which fetches many values at once, does not exist in v1. Use `snmpwalk`
Reading an object that does not exist returns `noSuchName`	The v1 error that corresponds to `noSuchObject` · `noSuchInstance` in v2c · v3
Writing a wrong value returns `badValue`	Corresponds to `wrongValue` · `wrongType` and similar in v2c · v3
Informs cannot be received	v1 has no Inform. Notifications arrive as Traps only (chapter 6)

The full mapping between v2c · v3 errors and v1 errors is under "Differences under v1" in AT Command Guide chapter 5.

3. Object addresses (OID)

An OID is an object's address. The manager finds objects by this address, not by their names (writeTest). That is why the snmpset in chapter 1 used 1.3.6.1.4.1.52942.3.0 instead of the name.

An OID is a series of numbers joined by dots, going from the broadest category on the left to the narrowest on the right. Split by position, the address of writeTest from chapter 1 looks like this:

 1.3.6.1.4.1 . 52942 . 3 . 0
 '----+----'   '-+-'   :   :
      :          :     :   :
      :          :     :   '-  marks an object with a single value. Always 0 (SNMP convention)
      :          :     '-----  object number. First argument of AT+OBJADD
      :          '-----------  company number assigned to the module's manufacturer (enterprise number)
      '----------------------  company area. The prefix shared by all companies

The spaces in the diagram are only for readability; the actual address is written without them, as 1.3.6.1.4.1.52942.3.0.

The standard object you read in chapter 1 (sysDescr) has an address that starts differently.

Object	Address	Start of the address
`sysDescr` (standard object)	`1.3.6.1.2.1.1.1.0`	`1.3.6.1.2.1` — standard objects common to all SNMP devices
`writeTest` (object you created)	`1.3.6.1.4.1.52942.3.0`	`1.3.6.1.4.1` — where each company places its own objects

Every object you create starts with 1.3.6.1.4.1.52942.

3.1 The default rule

If no OID is given in AT+OBJADD, the address is set automatically from the object number.

1.3.6.1.4.1.52942.<object number>.0

Command	Object address
`AT+OBJADD=1,"temperature",...`	`1.3.6.1.4.1.52942.1.0`
`AT+OBJADD=3,"writeTest",...`	`1.3.6.1.4.1.52942.3.0`

In most cases this rule is all you need. Sections 3.2 to 3.4 are needed only in specific cases.

3.2 Adding a product number

When one company uses this module in several products, their object addresses overlap. To tell the products apart, add a product number after the company number.

AT+PRODUCTARC=7

AT+SAVE

Objects created after this get the product number between the company number and the object number. Object 1, for example, gets this address:

 1.3.6.1.4.1.52942 . 7 . 1 . 0
 '-------+-------'   :   :   :
         :           :   :   :
         :           :   :   '-  always 0
         :           :   '-----  object number
         :           '---------▶ product number set with AT+PRODUCTARC=7
         '---------------------  up to the company number (as above)

The addresses of existing objects do not change, so decide on this before creating objects. If you set it only to try it out, restore it with AT+PRODUCTARC=0 and AT+SAVE. The rest of this guide assumes addresses without a product number. The full rules are in AT+PRODUCTARC.

3.3 Setting the address yourself

To use an address other than the default, give the OID as the last argument of AT+OBJADD.

AT+OBJADD=20,"inletTemp",Integer32,RO,VOLATILE,"1.3.6.1.4.1.52942.10.1.0"

AT+SAVE

Everything after the company number can be chosen freely.

 1.3.6.1.4.1.52942 . 10.1 . 0
 '-------+-------'   '+-'   :
         :            :     :
         :            :     '-  always 0
         :            '-------▶ the part you choose. Here 10 = temperature group, 1 = first sensor
         '--------------------  up to the company number (as above). Fixed

The address must start with 1.3.6.1.4.1.52942; otherwise it is refused with ERROR:OID_OUT_OF_SUBTREE. Addresses that are too long are also refused; the length limits are described in AT+OBJADD.

3.4 Identifying the end-product manufacturer

A manager reads sysObjectID (1.3.6.1.2.1.1.2.0) to identify the device's manufacturer and product. The default is the module manufacturer's number (1.3.6.1.4.1.52942), so management systems show the device as a product of the module manufacturer. Change it to the end-product manufacturer's number.

AT+SYSOBJID="1.3.6.1.4.1.12345.1.1"

AT+SAVE

 1.3.6.1.4.1 . 12345 . 1.1
 '----+----'   '-+-'   '+'
      :          :      :
      :          :      '--▶ product identification chosen by the manufacturer (e.g. line 1, model 1)
      :          '---------▶ end-product manufacturer's number, obtained from IANA
      '--------------------  company area (as above)

12345 is only an example; use the end-product manufacturer's actual number. If you set it only to try it out, restore the default with AT+SYSOBJID="" and AT+SAVE.

This setting changes only how the manufacturer is identified. Object addresses still start with 1.3.6.1.4.1.52942. Details are in AT+SYSOBJID.

The device description, name, contact and location that management systems show in their device lists can also be set with AT commands. Use them to tell devices apart when several are installed.

SNMP object	AT command	Example
sysDescr (device description)	`AT+SYSDESCR`	`AT+SYSDESCR="Acme UPS-3000 controller"`
sysName (device name)	`AT+SYSNAME`	`AT+SYSNAME="ups-lab-03"`
sysContact (contact)	`AT+SYSCONTACT`	`AT+SYSCONTACT="ops@example.com"`
sysLocation (location)	`AT+SYSLOCATION`	`AT+SYSLOCATION="Seoul HQ, B2, rack 4"`

The values can be read over SNMP right away; send AT+SAVE to keep them after a reboot. They are read-only over SNMP, so a manager cannot change them.

3.5 Checking object addresses

AT+OBJ?

The result looks like this:

+OBJ:1,"temperature",1.3.6.1.4.1.52942.1.0,Integer32,RO,VOLATILE,IMMEDIATE,""
+OBJ:3,"writeTest",1.3.6.1.4.1.52942.3.0,Integer32,RW,VOLATILE,IMMEDIATE,""
+OBJ:20,"inletTemp",1.3.6.1.4.1.52942.10.1.0,Integer32,RO,VOLATILE,IMMEDIATE,""

Object 1 from the Getting Started Guide, object 3 from chapter 1 and object 20 from 3.3 are listed in address order. The third value is the object's address, so this is where to look up the OID to use in the manager. The other values are explained in AT+OBJ?.

4. Registering many objects at once with a CSV file

When there are many objects, you can register the whole object table with a single CSV file instead of sending AT commands one line at a time. CSV files can be uploaded only on the web interface.

When the product is configured from the host MCU alone, without the web interface, create the objects with AT+OBJADD and set the same attributes as the CSV (set mode, range, unit, description, default) with AT+OBJATTR.

4.1 File format

The CSV template can be downloaded from the web interface (4.2, step 1). The first line contains the column names. The columns can be in any order, and the names are not case-sensitive.

object_id,name,oid,type,access,persistence,set_mode,min_value,max_value,unit,description,default_value
1,siteName,1.3.6.1.4.1.52942.1.0,OctetString,RW,PERSISTENT,IMMEDIATE,0,0,,Where this unit is installed,
2,deviceTemp,1.3.6.1.4.1.52942.2.0,Integer32,RO,VOLATILE,IMMEDIATE,-40,85,degC,Board temperature,0
3,humidity,1.3.6.1.4.1.52942.3.0,Gauge32,RO,VOLATILE,IMMEDIATE,0,100,%RH,Relative humidity,0
10,relayOut,1.3.6.1.4.1.52942.10.0,Integer32,RW,VOLATILE,CONFIRMED,0,1,,Relay; host must agree first,0
11,opMode,1.3.6.1.4.1.52942.11.0,Integer32,RW,PERSISTENT,IMMEDIATE,0,3,,0 off 1 auto 2 manual 3 svc,1

The line for object 2 in the example above, split into fields and numbered, looks like this. The numbers match the table below.

 2,deviceTemp,1.3.6.1.4.1.52942.2.0,Integer32,RO,VOLATILE,IMMEDIATE,-40,85,degC,Board temperature,0
 : '---+----' '---------+---------' '---+---' :  '--+---' '---+---' '+' :  '+-' '-------+-------' :
 1     2                3               4     5     6         7      8  9   10          11        12

No.	Column	Required	Values	If omitted	Example (object 2)
1	`object_id`	●	1 … 65535. The number the host uses in `AT+OBJVAL`	—	`2`
2	`name`	●	Up to 19 bytes	—	`deviceTemp`
3	`oid`	●	Numbers separated by dots, under `1.3.6.1.4.1.52942`	—	`1.3.6.1.4.1.52942.2.0`
4	`type`	●	`Integer32` `Unsigned32` `Gauge32` `Counter32` `Counter64` `TimeTicks` `OctetString` `IpAddress`	—	`Integer32`
5	`access`	●	`RO` · `RW`	—	`RO`
6	`persistence`		`VOLATILE` · `PERSISTENT`	`VOLATILE`	`VOLATILE`
7	`set_mode`		`IMMEDIATE` · `CONFIRMED` (chapter 5)	`IMMEDIATE`	`IMMEDIATE`
8	`min_value`		Integer. Smallest allowed value. See below	No limit	`-40`
9	`max_value`		Integer. Largest allowed value. See below	No limit	`85`
10	`unit`		Up to 7 bytes	Empty	`degC`
11	`description`		Up to 31 bytes. Longer text is cut and reported as a warning	Empty	`Board temperature`
12	`default_value`		Integer. Starting value of an integer object	0	`0`

A file with only the five required columns is enough.
min_value · max_value limit the value for numeric objects and the length for OctetString. Both 0 means no limit. An SNMP SET outside the range is refused with wrongValue. They do not apply to Counter64.
default_value takes integers only, so it cannot be used for string or IP address objects.
Enclose values that contain a comma in double quotes, and write a double quote inside a value as "".
A UTF-8 BOM saved by Excel, CRLF line endings and empty lines at the end of the file are fine as they are.
A line can be up to 512 bytes, with up to 16 columns.

4.2 Uploading

Upload the file on the OID mapping tab of the web interface. How to turn on the web interface is described in "Using the web interface" in the Getting Started Guide.

Click Download template to get the CSV template (oid_template.csv). It contains only the column names, so fill in one object per line as in the example in 4.1. To edit the object table currently in use, download it with Export active mapping instead.
Click the file button under Upload CSV and choose the filled-in file.
Click Validate only. The file is only checked, not applied, so the result ends with - not applied even when there are no errors.
If there are no errors, click Validate and apply. The file is applied when the result ends with - applied.

Check the applied objects on the Objects tab of the web interface. After applying the example in 4.1, it looks like this:

Objects tab

Value is the current value. No value has been written yet, so the CSV's default_value is shown. On the AT port, AT+OBJ? shows the same list.

If there are errors, the cause is shown for each line, and if any line has an error, nothing is applied. The existing object table is kept as it is.

6 rows, 1 objects, 5 errors - not applied
Row 3, Column oid: OID is outside the enterprise subtree
Row 4, Column type: unsupported object type

A large table of about 1000 objects takes about 20 seconds to upload and another 20 seconds to apply. Do not close the page until it finishes.

4.3 Things to know when applying

The whole object table is replaced by the CSV. Objects created with AT commands are also removed if the CSV does not include them.
The result is stored immediately, so no AT+SAVE is needed.
A value stored for a PERSISTENT object is restored only to its original object; it does not move to a different object that merely has the same number.
The uploaded CSV is kept on the module. The source shown by AT+OIDMAP? is then CSV_IMPORT, which changes to CSV_IMPORT_MODIFIED once objects are changed with AT commands.

4.4 Checking, re-applying and clearing with AT commands

A CSV can be uploaded only on the web interface, but checking, re-applying and clearing it afterwards can also be done with AT commands.

To	Web (`OID mapping` tab)	AT
Check the current mapping	Status line at the top of the tab	`AT+OIDMAP?`
Re-apply the stored CSV	`Re-apply stored CSV`	`AT+OIDMAPRELOAD`
Remove all user objects	`Clear mapping`	`AT+OIDMAPCLEAR="CONFIRM"`

Check — See how the object table was created and how many objects it has.

AT+OIDMAP?

After applying the example in 4.1, the result looks like this. The original size and CRC depend on the file.

+OIDMAP:CSV_IMPORT,5,1,<original size>,<original CRC32>,ACTIVE

Value	Meaning
`CSV_IMPORT`	Source of the object table. See the table below
`5`	Number of objects
`1`	Version of the CSV format
Original size · original CRC32	Size in bytes and check value of the stored CSV. Use them to tell which file was uploaded
`ACTIVE`	`ACTIVE` if objects exist, `EMPTY` if there are none

Source	Meaning
`DEFAULT`	No user objects
`MANUAL_AT`	Created with AT commands (`AT+OBJADD`)
`CSV_IMPORT`	Uploaded as a CSV on the web interface
`CSV_IMPORT_MODIFIED`	Uploaded as a CSV, then changed with AT commands

Re-apply — Rebuild the object table from the CSV stored on the module. Use this to return to the CSV state after changing objects with AT commands.

AT+OIDMAPRELOAD

If no CSV is stored, the result is ERROR:CSV_NOT_AVAILABLE. With many objects this takes a while, so wait for OK.

Clear — Remove all user objects. To prevent accidents, "CONFIRM" must be written exactly.

AT+OIDMAPCLEAR="CONFIRM"

Only the object table is emptied; the stored CSV is kept, so it can be applied again later with AT+OIDMAPRELOAD. Network settings, SNMPv3 users and communities stay as they are.

Starting a firmware update erases the stored CSV. The object table in use stays, but there is no longer a file to re-apply. If you manage objects with a CSV, upload the same CSV again after the update. A factory reset erases both the CSV and the object table.

5. Confirmed SET

For objects where writing a value makes the device actually do something, such as a relay, you can have the host MCU approve the manager's SET before it is applied. Write CONFIRMED in the CSV's set_mode column, or set it with an AT command. For example, to make object 10 a confirmed object:

AT+OBJATTR=10,SETMODE,CONFIRMED

AT+SAVE

When the manager sends a SET to such an object, the module asks the host with +SNMPSET:<request number>,<object>,<value>, and the host approves or refuses with AT+SETACK within 750 ms. The response format and rules are in AT+SETACK.

For example, when the manager writes 1 to object 10, this notification arrives on the AT port:

 +SNMPSET:27,10,1
          :  :  :
          :  :  :
          :  :  '-  value the manager wants to write
          :  '----  object number
          '-------  request number. Repeat it in AT+SETACK

To approve, answer with the same request number.

AT+SETACK=27,OK

To refuse, answer like this:

AT+SETACK=27,FAIL

6. Sending Traps and Informs

6.1 Traps and Informs

	Trap	Inform
Acknowledgement	None	Waits for the receiver's response
If delivery fails	The module cannot tell	Resent a set number of times, then `ERROR:NOTIFY_NO_RESPONSE`
v1	●	Not available
v2c	●	●
v3	●	● (with authentication, receiver keys must be registered, 6.5)

Up to 4 receivers can be registered, numbered 0 to 3.

6.2 Registering receivers

Register the receiver according to the SNMP version the manager uses. Follow only the one of the three subsections below that matches your manager. On the web interface, the same settings are on the Traps tab, and AT+TARGET? shows what is registered.

6.2.1 v3 receiver

Create a notification-only user (NOTIFICATION role) and register the receiver so that notifications are sent as that user.

AT+USMADD="trapuser",AUTHPRIV,SHA256,"trapauth123",AES128,"trappriv123",NOTIFICATION

AT+TARGETADD=0,"192.168.0.20",162,"trapuser",AUTHPRIV

The arguments of the command above are:

 AT+TARGETADD=0,"192.168.0.20",162,"trapuser",AUTHPRIV
              : '-----+------' '+' '---+----' '--+---'
              :       :         :      :         :
              :       :         :      :         '-----  security level
              :       :         :      '---------------  user
              :       :         '----------------------▶ port the notifications go to. Usually 162
              :       '--------------------------------▶ address of the manager PC that receives notifications
              '----------------------------------------▶ receiver number (0 to 3)

AT+SAVE

6.2.2 v2c receiver

A v2c receiver takes a version and a community instead of a user and security level. First register the community to use for notifications.

AT+COMMADD="trap-c",NOTIFICATION

AT+TARGETADD=1,"192.168.0.20",162,"",,TRAP,3,1000,V2C,"trap-c"

v2c has no user or security level, so those two positions are left empty. The commas stay so that the remaining arguments keep their positions.

 AT+TARGETADD=1,"192.168.0.20",162,"",,TRAP,3,1000,V2C,"trap-c"
              : '-----+------' '+' : : '+-' : '+-' '+' '--+---'
              :       :         :  : :  :   :  :    :     :
              :       :         :  : :  :   :  :    :     '-----  community
              :       :         :  : :  :   :  :    '-----------▶ version (V1, V2C or V3)
              :       :         :  : :  :   :  '----------------▶ response timeout in ms (Inform only)
              :       :         :  : :  :   '-------------------▶ retries (Inform only)
              :       :         :  : :  '-----------------------▶ kind (TRAP or INFORM)
              :       :         :  : '--------------------------  security level (empty)
              :       :         :  '----------------------------  user (empty)
              :       :         '-------------------------------  port
              :       '-----------------------------------------  manager PC address
              '-------------------------------------------------  receiver number

Retries and the response timeout are used by Informs only. If an Inform gets no response within the timeout, it is resent up to the number of retries. Traps do not wait for a response, so these two values are not used for them.

AT+SAVE

Whether a Trap or an Inform is sent is decided by the sending command, not at registration (6.3). One receiver can therefore get both Traps and Informs. To change the Inform retries and response timeout, register the same number again.

AT+TARGETADD=1,"192.168.0.20",162,"",,INFORM,5,2000,V2C,"trap-c"

AT+SAVE

6.2.3 v1 receiver

The same as v2c, with V1 as the version. Register the community first if it does not exist; if you created trap-c in 6.2.2, skip this command.

AT+COMMADD="trap-c",NOTIFICATION

AT+TARGETADD=3,"192.168.0.20",162,"",,TRAP,3,1000,V1,"trap-c"

AT+SAVE

v1 has no Inform. Registering a V1 receiver as INFORM is refused with ERROR:NOT_SUPPORTED, and AT+INFORMSEND is not delivered to v1 receivers. Use only AT+TRAPSEND for v1 receivers.

6.3 Sending

To send a Trap:

AT+TRAPSEND=1001,2

To send an Inform:

AT+INFORMSEND=1001,2

The notification is sent to every registered receiver, as a Trap or an Inform according to the command, regardless of the TRAP · INFORM given at registration. Both commands take the same arguments.

To send an Inform to a v3 receiver (6.2.1), the keys in 6.5 must be registered first. Without them, nothing is sent to that receiver and the result is ERROR:ACCESS_DENIED.

Argument	Meaning
First (`1001`)	Notification number. Chosen by the host to tell kinds of notification apart
Second (`2`, optional)	Object number to include. Its OID and current value are carried in the notification

6.3.1 Contents of a v2c or v3 notification

What the manager receives when no product number (3.2) is used:

Variable	Value
`sysUpTime.0`	Module uptime
`snmpTrapOID.0`	`1.3.6.1.4.1.52942.1001` (company number + [product number] + notification number)
OID of object 2	Current value of object 2

Split up, the value of snmpTrapOID.0 looks like this. Unlike an object address, it does not end in .0.

 1.3.6.1.4.1.52942 . 1001
 '-------+-------'   '+-'
         :            :
         :            '---▶ notification number. First argument of AT+TRAPSEND
         '----------------  up to the company number (as in chapter 3)

6.3.2 Contents of a v1 notification

A v1 Trap uses a different format: the notification number is not appended to the OID but carried in a separate field. Instead of the snmpTrapOID.0 and sysUpTime.0 variables, the same information is in the fields below.

v1 Trap field	Value
enterprise	`1.3.6.1.4.1.52942` (up to the product number if `AT+PRODUCTARC` is used)
agent-addr	IP address the module is using now
generic-trap	`6` (enterpriseSpecific — a notification defined by the company)
specific-trap	Notification number (first argument of `AT+TRAPSEND`, e.g. `1001`)
time-stamp	Module uptime
Variable	OID and current value of object 2

The manager identifies the kind of notification from the enterprise and specific-trap values.

6.4 Receiving on the manager (net-snmp `snmptrapd`)

On the manager PC, snmptrapd receives the notifications. Its configuration file is /etc/snmp/snmptrapd.conf on Ubuntu · Debian; add the settings for the version you registered in 6.2.

6.4.1 Receiving v3 notifications

createUser -e 0x8000CECE030008DC123456 trapuser SHA-256 trapauth123 AES trappriv123
authUser log trapuser

For a v3 Trap the module is the authoritative engine, so createUser -e takes the module's engine ID. Read it with the command below and put 0x in front of the value.

AT+ENGINEID?

The result looks like this:

+ENGINEID:"8000CECE030008DC123456"

6.4.2 Receiving v2c and v1 notifications

Configure snmptrapd to log notifications that arrive with the community trap-c. This one line covers both v2c and v1.

authCommunity log trap-c

6.4.3 Running it

After changing the configuration, restart the service. For a first check, it is easier to stop the service and run snmptrapd directly, so that received notifications appear on screen right away.

sudo systemctl stop snmptrapd

sudo snmptrapd -f -Lo

If the first command gives an error such as System has not been booted with systemd, no service is running and you can ignore it. Port 162 requires sudo. To receive notifications in WSL, first apply the WSL setting in chapter 0.

6.5 Authenticated v3 Informs

For a v3 Inform, unlike a Trap, the receiver is the authoritative engine. To send v3 Informs with authentication (AUTHNOPRIV · AUTHPRIV), keys computed with each receiver's engine ID must be registered with AT+TARGETKEY. The module does not store passwords, so it cannot compute these keys itself.

How to compute and register the keys is described in inform_keys.md (Korean). Without keys, no notification is sent and the result is ERROR:ACCESS_DENIED.

If this is too much effort, use v3 Traps (no keys needed) or v2c Informs.

6.6 When sending fails

A failure is reported with ERROR:<code> and +NOTIFYFAIL:<receiver>,<reason>. The causes for each code are in AT Command Guide chapter 8 and chapter 12.

A Trap is not acknowledged, so OK from the module does not mean it reached the manager. Check the manager's log to confirm delivery.

7. Troubleshooting

If the module does not communicate at all, the manager shows Unknown user name, or settings disappear after a reboot, see Troubleshooting in the Getting Started Guide first. The table below covers problems that can occur while following this guide.

Symptom	What to check
`Authentication failure` on v3 requests	The password or algorithm (SHA-1 / SHA-256) differs from the manager's. The `USM` line of `AT+DIAG?` counts the failures
`Timeout` on v1 · v2c requests	The version is off (`AT+SNMPVER?`) or the community is wrong (`AT+COMM?`). The module does not answer such requests
`noCreation` on a SET	No object exists at that OID. Check objects and OIDs with `AT+OBJ?`, and create it with `AT+OBJADD` if missing
`noAccess` · `notWritable` on a SET	The object is `RO`, or the user's or community's role is `MONITOR` or `NOTIFICATION`
`wrongValue` on a SET	The value is outside the object's allowed range (the CSV's `min_value` · `max_value`, or `RANGE` in `AT+OBJATTR`)
A SET fails after 750 ms	The object is `CONFIRMED` and the host did not send `AT+SETACK`
CSV shows `not applied`	Fix the lines named by `Row` and `Column` in the result. Nothing is applied while any error remains
Traps do not arrive	Check address, port and version with `AT+TARGET?`, and on the manager the firewall (UDP 162) and `snmptrapd.conf`

Document	Contents
Getting Started Guide	Wiring, IP setup, first SNMPv3 read, turning on the web interface
AT Command Guide	Every AT command
`inform_keys.md` (Korean)	Computing and registering receiver keys for authenticated v3 Informs
Firmware Update Guide	Firmware update

0. Installing the SNMP manager​

Linux​

Windows​

macOS​

Checking the installation​

When results show only numbers​

Using a graphical tool​

1. Reading and writing with SNMPv3​

2. Turning on SNMPv1 and v2c​

2.1 Registering communities​

2.2 Reading and writing with v2c​

2.3 Reading and writing with v1​

3. Object addresses (OID)​

3.1 The default rule​

3.2 Adding a product number​

3.3 Setting the address yourself​

3.4 Identifying the end-product manufacturer​

3.5 Checking object addresses​

4. Registering many objects at once with a CSV file​

4.1 File format​

4.2 Uploading​

4.3 Things to know when applying​

4.4 Checking, re-applying and clearing with AT commands​

5. Confirmed SET​

6. Sending Traps and Informs​

6.1 Traps and Informs​

6.2 Registering receivers​

6.2.1 v3 receiver​

6.2.2 v2c receiver​

6.2.3 v1 receiver​

6.3 Sending​

6.3.1 Contents of a v2c or v3 notification​

6.3.2 Contents of a v1 notification​

6.4 Receiving on the manager (net-snmp snmptrapd)​

6.4.1 Receiving v3 notifications​

6.4.2 Receiving v2c and v1 notifications​

6.4.3 Running it​

6.5 Authenticated v3 Informs​

6.6 When sending fails​

7. Troubleshooting​

Related documents​

0. Installing the SNMP manager

Linux

Windows

macOS

Checking the installation

When results show only numbers

Using a graphical tool

1. Reading and writing with SNMPv3

2. Turning on SNMPv1 and v2c

2.1 Registering communities

2.2 Reading and writing with v2c

2.3 Reading and writing with v1

3. Object addresses (OID)

3.1 The default rule

3.2 Adding a product number

3.3 Setting the address yourself

3.4 Identifying the end-product manufacturer

3.5 Checking object addresses

4. Registering many objects at once with a CSV file

4.1 File format

4.2 Uploading

4.3 Things to know when applying

4.4 Checking, re-applying and clearing with AT commands

5. Confirmed SET

6. Sending Traps and Informs

6.1 Traps and Informs

6.2 Registering receivers

6.2.1 v3 receiver

6.2.2 v2c receiver

6.2.3 v1 receiver

6.3 Sending

6.3.1 Contents of a v2c or v3 notification

6.3.2 Contents of a v1 notification

6.4 Receiving on the manager (net-snmp `snmptrapd`)

6.4.1 Receiving v3 notifications

6.4.2 Receiving v2c and v1 notifications

6.4.3 Running it

6.5 Authenticated v3 Informs

6.6 When sending fails

7. Troubleshooting

Related documents