The document provides instructions on how to install and configure SNMP on RHEL 7. It describes downloading the required packages, editing the configuration file, opening the required port in the firewall, and testing SNMP queries locally and remotely. SNMP can be used to monitor devices and retrieve statistics on parameters like performance, usage, and storage. The three main versions of SNMP are also outlined, highlighting their features around security, querying, and remote configuration capabilities.

1. How To Install and Configure SNMP on RHEL 7
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Table of Contents
Overview.......................................................................................................................................................1
Applies To......................................................................................................................................................1
Pre-Requisites ...............................................................................................................................................1
Installation and Configuration procedure.....................................................................................................1
Check Package...........................................................................................................................................1
Install Package...........................................................................................................................................1
Verify Installation......................................................................................................................................2
SNMP – Configuration File........................................................................................................................2
Default Configuration File – Snippet.....................................................................................................2
Firewall Configuration...................................................................................................................................3
Firewall Configuration – Open UDP Port ..................................................................................................3
Firewall Configuration – Reload................................................................................................................3
Firewall Configuration – List .....................................................................................................................3
snmpwalk – localhost Query.....................................................................................................................4
snmpwalk – Remote Query.......................................................................................................................4
SNMP Configuration .....................................................................................................................................5
Listening address ......................................................................................................................................5
SNMP Daemon Management .......................................................................................................................5
Troubleshooting............................................................................................................................................6
Timeout: No Response from 127.0.0.1.....................................................................................................6
Error Message.......................................................................................................................................6
Cause.....................................................................................................................................................6
Resolution .............................................................................................................................................6
SNMP Version Features ................................................................................................................................7

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Overview
SNMP stands for “Simple Network Management Protocol”, it can be utilized to monitor any devices that
support snmp, few of the devices are server, router, network printers, firewalls. SNMP can monitor a
variety of parameters for these devices such as server performance, network usage, disk utilization.
Applies To
Tested on RHEL 7, CentOS 7, though it can be configured on most of the *nix flavor of OS.
Pre-Requisites
 snmp, snmp-utils
Installation and Configuration procedure
First of all, we will check if the package is already installed else we will install the packages.
Check Package
Check if the package is already installed, to check package installation status, run the command;
rpm -qa | grep net-snmp net-snmp-utils
Install Package
After checking the package installation status, if the package is not installed. Install the package to install
run the command;
yum install net-snmp net-snmp-utils -y

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Verify Installation
After installing the net-snmp packages verify if the package is installed, to check package installation
status, run the command;
rpm -qa | grep net-snmp*
SNMP – Configuration File
Default configuration file that is configured as per the below. To display current configuration without
comments and lines non-blank lines, run command;
grep -v "^$" /etc/snmp/snmpd.conf | grep -v '^ *#'
Default Configuration File – Snippet
com2sec notConfigUser default public
group notConfigGroup v1 notConfigUser
group notConfigGroup v2c notConfigUser
view systemview included .1.3.6.1.2.1.1
view systemview included .1.3.6.1.2.1.25.1.1
access notConfigGroup "" any noauth exact systemview none none
syslocation Unknown (edit /etc/snmp/snmpd.conf)
syscontact Root <root@localhost> (configure /etc/snmp/snmp.local.conf)
dontLogTCPWrappersConnects yes

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Firewall Configuration
SNMP protocol works on UDP port “161” and this port needs to be opened in order to listen and scan the
report from remote servers and for latest version of snmp service supports running on TCP port which is
again on “161”.
Firewall Configuration – Open UDP Port
After installing and checking the default configuration, the next step that needs to be done is to open
firewall port, snmp protocol run on UDP port 161.
firewall-cmd --permanent --add-port=161/udp
Firewall Configuration – Reload
Reload the firewall configuration.
firewall-cmd --reload
Firewall Configuration – List
After reloading firewall daemon, list the current rules set.
firewall-cmd --list-all

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snmpwalk – localhost Query
After configuring the firewall, you can go ahead and test the snmp query data on the localhost it should
be able to retrieve the OID values when you run. To retrieve the information run the command;
snmpwalk -v 1 -c public -O e 127.0.0.1
snmpwalk – Remote Query
To query from a remote client to retrieve the OID values when you run. To retrieve the information run
the command; in this case we are querying from a windows machine.
snmpwalk -r:54.165.245.172 -q -c:public

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SNMP Configuration
In order to SNMP to work for any query requests, it should be configured only agentaddress directives is
listed and configured, similarly other directives can be configured according to the business needs.
Listening address
This attribute will associate the IP address wherein the snmp service will listen on.
Attribute Name IP Address Information Port
agentaddress 127.0.0.1 161
agentaddress IP Address 161
agentaddress 127.0.0.1:161
SNMP Daemon Management
State Command Purpose
Enable systemctl enable snmpd Enable the service to start at boot and start automatically
Start systemctl start snmpd Start the service
Stop systemctl stop snmpd Stop the service
Restart systemctl restart snmpd Restart the service
Disable systemctl disable snmpd Disable the service to start at upon booting
Mask systemctl mask snmpd Masking the service to disable dynamic and manual
starting.

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Troubleshooting
Timeout: No Response from 127.0.0.1
Error Message
Timeout: No Response from 127.0.0.1
Cause
One of the cause is the service is not running, start the service.
Another cause is when the remote server doesn’t have port is blocked or not listening default port on the
client.
systemctl status snmpd
Resolution
To resolve the issue we will start the daemon and query again for the first cause, for the second cause
ensure firewall port is configured such that UDP port 161 is opened and listening, check firewall
configuration section.
systemctl start snmpd

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SNMP Version Features
SNMP has 3 versions currently, that can be configured based on the business needs. The below table will
give insight into different versions and its features that provide device statistics.
SNMP Version Features
Version 1 This provides device statistics and error reporting without consuming a lot of system
resources. Security was limited to community strings and access controls based on
the IP address of the querying server. Data communication wasn't encrypted.
Version 2 This is referred to as v2c which expanded the number of supported error codes,
increased the size of counters used to track data, and has the ability to do bulk
queries that more efficiently loaded response packets with data
Version 3 This version provides greater security and remote configuration capabilities than
earlier versions.
Access is not only limited to a single community string for read-only and read/write
access, as usernames and passwords can also be configured in this version.
Support for encrypted SNMP data transfer and transfer error detection is also
provided.