SNMPv3 on Ubuntu/Debian for PRTG Monitoring

17 October 2025

1. Install

sudo apt update
sudo apt install -y snmp snmpd snmp-mibs-downloader libsnmp-dev

2. Create the SNMPv3 user (with snmpd stopped)

sudo systemctl stop snmpd
sudo net-snmp-create-v3-user -ro -A 'AUTH_PASS' -X 'PRIV_PASS' -a SHA -x AES snmp_user

-ro: read-only.
-A / -a SHA: authentication password and algorithm.
-X / -x AES: privacy (encryption) password and algorithm.
Passwords must be at least 8 characters.

3. Configure the agent

Back up /etc/snmp/snmpd.conf and replace its content with:

# SNMPv3 only - monitored by PRTG
agentAddress udp:SERVER_IP:161
rouser snmp_user authPriv

sysLocation    Datacenter / rack
sysContact     Admin <support@example.com>
sysName        server-name

Don't put the passwords in this file: the user was already created in step 2.

In /etc/snmp/snmp.conf comment out the mibs : line so the tools load the downloaded MIBs.

4. Start and test

sudo systemctl enable --now snmpd
sudo ss -ulnp | grep 161
snmpwalk -v3 -l authPriv -u snmp_user -a SHA -A 'AUTH_PASS' -x AES -X 'PRIV_PASS' SERVER_IP system

If snmpwalk returns data, the agent is working.

5. Firewall

Allow only the PRTG server:

sudo ufw allow proto udp from PRTG_IP to any port 161

6. PRTG

In the device settings, Credentials for SNMP Devices:

SNMP Version: v3
Authentication Type: SHA
User: snmp_user
Password: the authentication password
Encryption Type: AES
Data Encryption Key: the privacy password

Then add the SNMP sensors (CPU, memory, disk, traffic).