Linux SNMP Configuration and Troubleshooting Guide

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    Overview

    These 4 commands are based on CentOS. These should work for most other distros too.

    Since the default snmpd.conf file can contain a lot of info I'm going to create the simplest conf we can to minimize errors. The snmpd.conf file lives in /etc/snmp/ on most linux distros.

     

    Prerequisites

    If you haven't already installed snmp on your linux server then you'll want to grab both the net-snmp and net-snmp-utils packages. If you don't know the exact distro that you're running then use this command: cat /etc/*-release

    CentOS 6 or older: yum install net-snmp net-snmp-utils

    CentOS 7: dnf install net-snmp net-snmp-utils

    Ubuntu: apt-get install snmp

     

    Configuration

    Backup original snmpd.conf file

    mv /etc/snmp/snmpd.conf /etc/snmp/snmpd.conf.bak

    Create a new snmpd.conf file and populate it with a single line.

    touch /etc/snmp/snmpd.conf

    echo "rocommunity public" > /etc/snmp/snmpd.conf

    Restart the SNMP service.

    service snmpd restart

     

    If snmp works after the configuration above then it is either an misconfigured snmpd.conf file or snmp view limitations. If you prefer, you can leave the new snmpd.conf file in place.

     

    Troubleshoot

    If the above configuration does not fix the issues then try these steps

    • Test if snmp is listening. Replace public with your community string. If this works then the screen should fill with lots of SNMP info.
      • command: snmpwalk –v2c –c public localhost
    • Test if iptables (firewall) is running.
      • command: service iptables status
        • If it is running, try service iptables stop and then test snmp from Orion again.
        • If it works with iptables off then add some rules to iptables to allow it instead of keeping it off. Shout out to animelov for the commands/help!
          • iptables -I INPUT -p udp -m udp --dport 161 -j ACCEPT

          • iptables -I INPUT -p udp -m udp --dport 162 -j ACCEPT

          • iptables-save > /etc/sysconfig/iptables

          • service iptables restart

    • If Orion still cannot connect to SNMP on the device the there is a firewall in-between Orion and the Linux host.