Resolving SNMP MIB Syntax Errors in Ubuntu: A Comprehensive Debugging Guide


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When working with SNMP on Ubuntu systems, many administrators encounter puzzling MIB syntax errors despite using the official package repositories. The core issue manifests when running basic SNMP commands like:

snmptranslate -IR -On sysDescr
snmpwalk -v2c -c public localhost system

These commands produce operational output but simultaneously report syntax issues in MIB definitions. The errors typically fall into several categories:

  • Missing or incorrect imports (e.g., mib-2 not imported)
  • Parse errors in IANA-registered MIBs
  • OID linkage problems between dependent MIBs

The primary culprits behind these MIB issues are:

1. Package version mismatches between snmpd and MIBs
2. Incomplete MIB collections from upstream sources
3. Legacy MIBs that haven't been updated for modern parsers
4. Missing dependency declarations in MIB packages

To verify your current MIB setup:

# Check installed MIB versions
dpkg -l | grep -E 'snmp|mibs'

# List loaded MIBs
snmptranslate -Dparse-mibs 2>&1 | grep Loading

Option 1: Manual MIB Correction

For the specific IPATM-IPMC-MIB error, edit the file:

sudo nano /usr/share/mibs/ietf/IPATM-IPMC-MIB

Add the missing import at the beginning:

IMPORTS
    mib-2 FROM SNMPv2-SMI;

Option 2: Alternative MIB Sources

Consider using more maintained MIB collections:

wget http://www.circitor.fr/Mibs/MibIndices.php?arch=all -O /tmp/mibs.zip
sudo unzip /tmp/mibs.zip -d /usr/share/mibs/custom/

Then update /etc/snmp/snmp.conf:

mibdirs +/usr/share/mibs/custom
mibs +ALL

Create a validation script (check_mibs.sh):

#!/bin/bash
for mib in $(find /usr/share/mibs -name "*.txt" -o -name "*.mib"); do
    echo "Validating $mib..."
    smilint -l 6 $mib
done 2>&1 | tee mib_validation.log

For production systems, implement these changes:

# Create override directories
sudo mkdir -p /etc/snmp/mibs/{corrected,disabled}

# Add to snmp.conf
echo "mibdirs /etc/snmp/mibs/corrected:/usr/share/mibs/ietf" | sudo tee -a /etc/snmp/snmp.conf
echo "mibdirs /usr/share/mibs/iana" | sudo tee -a /etc/snmp/snmp.conf

When working with SNMP on Ubuntu, you might encounter syntax errors in MIB files despite using the standard installation method:

sudo apt-get install snmp-mibs-downloader
sudo download-mibs

These errors typically appear during snmpwalk or snmptranslate operations and indicate problems with the MIB definitions. Common error patterns include:

Bad operator (INTEGER)
Unlinked OID
Undefined identifier
Expected token errors
Bad object identifier

The primary reasons for these errors are:

  • Incomplete or outdated MIB packages from repositories
  • Missing dependencies between MIB files
  • Version mismatches between different MIB files
  • Improper MIB file loading order

First, verify your MIB configuration with:

snmptranslate -Dparse-mibs 2>&1 | grep "MIB search path"

This will show you where Net-SNMP is looking for MIB files. The standard location should be /usr/share/mibs.

For the specific error Unlinked OID in IPATM-IPMC-MIB: marsMIB ::= { mib-2 57 }, the solution is to ensure proper imports:

# Edit the problematic MIB file
sudo nano /usr/share/mibs/ietf/IPATM-IPMC-MIB

# Add the missing import at the beginning of the file
IPATM-IPMC-MIB DEFINITIONS ::= BEGIN
IMPORTS
    mib-2 FROM SNMPv2-SMI;

If the Ubuntu repository MIBs continue to cause problems, consider:

  1. Downloading directly from IETF: 
    wget https://www.iana.org/assignments/ianaxwhatever-mib/ianaxwhatever-mib
  2. Using the Net-SNMP maintained MIBs: 
    git clone https://github.com/net-snmp/net-snmp
cp -r net-snmp/mibs /usr/share/mibs/snmp

Instead of using mibs +ALL, which can cause loading issues, try:

# /etc/snmp/snmp.conf
mibdirs /usr/share/mibs/ietf:/usr/share/mibs/iana
mibs IF-MIB:IP-MIB:TCP-MIB:UDP-MIB

This selective loading approach often resolves many parsing issues while maintaining full functionality.

For thorough validation of your MIB collection:

# Install smilint for MIB validation
sudo apt-get install libsnmp-dev smilint

# Validate all MIBs
find /usr/share/mibs -type f -name "*.txt" -exec smilint -l 6 {} \;

This will provide detailed reports of all syntax issues in your MIB files.

For persistent issues with specific MIBs, you might need to:

# Create a local override directory
sudo mkdir /usr/share/mibs/local

# Copy and fix problematic MIBs
sudo cp /usr/share/mibs/ietf/IPATM-IPMC-MIB /usr/share/mibs/local
sudo nano /usr/share/mibs/local/IPATM-IPMC-MIB

# Update your snmp.conf
mibdirs +/usr/share/mibs/local