SNMP Error: Session Terminated Due to Invalid IP Address in Switch Response

Guide to Solving the SNMP Error: “Invalid IP Address” in vNode

Problem Description

When using the SNMP module in vNode to communicate with a switch or other network device, an error may occur that unexpectedly interrupts the SNMP session. This behavior typically appears after a few minutes of normal operation (around 5 minutes), at which point the session is suddenly closed and communication is lost.

In the system logs, you may see a message similar to:

WARN | Session/CMTO1 -> A connection error occurs. Session will be closed: ResponseInvalidError: Length '16' of IP address '00000000000000000000000000000000' is not 4

DEBUG | Session/CMTO1 -> Error ending walk request: Error: Socket forcibly closed

TRACE | Session/CMTO1 -> Session and socket closed!

Cause of the Error

This issue occurs because vNode receives an invalid IP address from the SNMP device. Instead of a valid IPv4 address (e.g., 192.168.1.1), the device responds with a malformed address consisting entirely of zeros:

00000000000000000000000000000000

Since vNode expects a valid 4-byte IPv4 address, this malformed response causes a decoding failure, which forces the SNMP session to close automatically.

• Common scenarios where this error may occur:

• After maintaining an active SNMP session for several minutes of continuous polling (usually between 3 to 5 minutes).

• When performing operations such as walkRequest or getRequest on OIDs whose return values include an invalid or empty IP.

• On devices that have limitations in handling multiple simultaneous SNMP requests, or that are misconfigured.

•     When querying specific OIDs that are not properly defined or supported by the SNMP device, leading to unexpected or incorrect responses.

✅ Solution for SNMP "Invalid IP Address" Error in vNode

Cause of the issue:

The error occurs because the SNMP device is sending an ipAddress-type value with an incorrect format. Instead of the expected 4 octets for a valid IPv4 address, the device returns 16 octets, which causes vNode to terminate the session due to an invalid response.

Technical solution:

A new version of the SnmpClient module has been developed, which now handles these malformed responses without closing the connection. This improves communication stability and removes the need to restart the module when such errors occur.

You can download the updated SnmpClient module from the following link:

SnmpClient-main-1.2.6-250514.1206-nightly-41e8ed60.n3b 

Steps to apply the fix:

1. Stop the vNode Bootstrap service

• Open the Windows Services Panel (services.msc)
• Locate the service named vNode Bootstrap
• Right-click and select “Stop”

        2. Replace the module file

• Navigate to: C:\Program Files\vNode\bin\modules\SnmpClient
• Replace the existing file with the new one you downloaded from OneDrive

        3. Restart the service

• Go back to the Services Panel
• Right-click vNode Bootstrap and select “Start”

        4. Verify the connection

• Open vNode and confirm that communication with the SNMP device has been restored successfully

Additional recommendation:

Although the updated module prevents the error from breaking the connection, it is strongly recommended to contact the SNMP device manufacturer to review the configuration or update the device firmware. This will help avoid malformed SNMP data that doesn't comply with the protocol standard.

Created by JF