MRTG Make sure snmp server configured properly

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Step # 3 : Make sure snmp server configured properly

Run the snmpwalk command to request for tree of information about network entity. In simple words, query the snmp server for your IP address (assigned to your eth0, eth1, lo interface by Linux):

# snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex
Sample outputs: 
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.127.0.0.1 = 1
ip.ipAddrTable.ipAddrEntry.ipAdEntIfIndex.192.168.0.3 = 2

If you see your IP address, proceed to step 4; else it is a time to configure snmp server as follows (by default RHEL and older Redhat v8/9 are not configured for snmp server for security reason):

Configure SNMP

(1) Edit the file /etc/snmp/snmpd.conf using a text editor such as vi, enter: 
# vi /etc/snmp/snmpd.conf

Change/Modify line(s) as follows:

Find the following Line:

com2sec notConfigUser  default       public
Replace with (make sure you replace 192.168.0.0/24 with your network/subnet) the following lines: 
com2sec local     localhost           public
com2sec mynetwork 192.168.0.0/24      public

Scroll down a bit and change :

Find Lines:

group   notConfigGroup v1           notConfigUser
group   notConfigGroup v2c           notConfigUser

Replace with:

group MyRWGroup v1         local
group MyRWGroup v2c        local
group MyRWGroup usm        local
group MyROGroup v1         mynetwork
group MyROGroup v2c        mynetwork
group MyROGroup usm        mynetwork

Again scroll down a bit and locate the following line:

Find line:

view    systemview     included      system

Replace with:

view all    included  .1                               80

Again scroll down a bit and change the following line:

Find line:

access  notConfigGroup ""      any       noauth    exact  systemview none none

Replace with:

access MyROGroup ""      any       noauth    exact  all    none   none
access MyRWGroup ""      any       noauth    exact  all    all    none

Scroll down a bit and change the following lines:

Find lines:

syslocation Unknown (edit /etc/snmp/snmpd.conf)
syscontact Root  (configure /etc/snmp/snmp.local.conf)
Replace with (make sure you supply appropriate values): 
syslocation Linux (RH3_UP2), Home Linux Router.
syscontact YourNameHere <you@example.com>

For your convenient, here is my /etc/snmp/snmpd.conf file. Feel free to use this file. Make sure you make a backup of your existing file.

Start your snmp server and test it:

(a) Make sure when linux comes up snmpd always starts after the system reboot:

 # chkconfig snmpd on

(b) Start the snmpd service:

 # service snmpd start

(c) Finally, test your snmp server:

 # snmpwalk -v 1 -c public localhost IP-MIB::ipAdEntIfIndex
Install mrtg if not installed
Determine if snmp server is running or not