Check SNMP Connectivity to a Network Device

Network Monitoring

How to Check SNMP Connectivity to a Network Device

Verify that the Probe can reach a network device and poll it using SNMP v2c or SNMP v3 credentials.

Overview

Use this guide when a network device does not return data in Cloudmon, or before adding a new device for SNMP monitoring. Run these checks from the Probe that polls the device.

The test has three steps: confirm the device is reachable with ping, then query the device using SNMP v2c or SNMP v3.

Prerequisites

IP address of the target network device.
SNMP credentials (v2c community string or v3 security credentials).
snmpwalk or snmpget utility installed on the Probe.
ICMP and UDP port 161 allowed between the Probe and the device.

Step 1: Check Device Reachability

Run the following command from the Probe after replacing the placeholder:

ping <DEVICE_IP>

Example:

ping 192.168.1.10

A successful response shows replies from the device with round-trip times. On Linux, press Ctrl + C to stop the ping, or use ping -c 4 <DEVICE_IP> to send four packets only.

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Note: Some devices and firewalls block ICMP. If ping fails, continue with the SNMP test. A device can still respond to SNMP when ping is blocked.

Step 2: Test SNMP v2c

Run the following command after replacing the placeholders:

snmpwalk -v2c -c '<COMMUNITY>' <DEVICE_IP> 1.3.6.1.2.1.1

Example:

snmpwalk -v2c -c 'public' 192.168.1.10 1.3.6.1.2.1.1

Step 3: Test SNMP v3

For the authPriv security level, run:

snmpwalk -v3 -l authPriv \
  -u '<USERNAME>' \
  -a SHA -A '<AUTH_PASSWORD>' \
  -x AES -X '<PRIV_PASSWORD>' \
  <DEVICE_IP> 1.3.6.1.2.1.1

Replace the security level and the authentication and privacy algorithms with those configured on the device. For authNoPriv or noAuthNoPriv, use the matching -l option and omit the credentials that level does not use.

Expected Results

Result	What to check
Success	System information such as device description, hostname, and uptime is returned. No action needed.
Ping fails	Check that the device is powered on, the IP address is correct, and routing between the Probe and the device is in place. Check whether ICMP is blocked by a firewall.
Timeout	Check device reachability, firewall rules, UDP port 161, and the SNMP configuration on the device.
Authentication failure	Verify the community string, or the SNMP v3 username, security level, passwords, and algorithms.
No output or authorization error	Verify that the SNMP user or community has permission to access the requested OIDs.

Important Notes

Run all commands from the same Probe that performs SNMP polling for the device.
Ensure SNMP is enabled on the device and permits requests from the Probe's source IP.

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Security: Do not share credentials in logs, screenshots, or support tickets. Use SNMP v3 where stronger authentication and encryption are required.

Check SNMP Connectivity from a Cloudmon Probe | Cloudmon