Get the most of NetScanner, enable SNMP on your devices


What is SNMP?

SNMP (Simple Network Management Protocol) is a networking protocol that is mostly used to monitor network devices. SNMP is a standard and is very well supported by many many devices (MS Windows desktop and servers, all unix flavors you can think of including MAC OS X, Cisco IOS, Juniper junOS, etc...) .

The data accessed via SNMP is structured in sections called MIBs (Management Information Base). SNMP has 3 versions, SNMPv1 and SNMPv2 are very similar and are the most widely used, NetScanner can use both SNMPv1 and SNMPv2.
SNMPv1 and SNMPv2 security is based on a shared secret between the server and the client called a "community". The SNMP community is a plain text string that acts both as a user-name (for access control) and as a password (for authentication).

More information about SNMP:

NetScanner uses SNMP to gather and show you information about your network devices, it only requires read access (a read community).

For NetScanner or any other SNMP client to be able to collect this information, the scanned devices must be running an SNMP agent (server), and the device firewall must let UDP traffic go through on port 161.

Information NetScanner fetches from your devices:

  • System information about a device such as the OS installed on it, its name, how long it has been running, etc... (located in the system MIB)
  • Network interface list and bandwidth utilization (information located in the interface MIB and the IF-X MIB)
  • CPU information and percent utilization (information located in the host-resource MIB)
  • Memory list and memory usage (information located in the host-resource MIB)
  • Hard Disk list and Hard Disk space usage (information located in the host-resource MIB)

How can I enable and configure SNMP on my devices?

Enable SNMP on Linux

Enable SNMP on BSD

Enable SNMP on MAC OS X

The net-snmp agent comes already pre-installed with MAC OSX, you only have to configure /etc/snmp/snmpd.conf (see "Typical snmpd.conf for Net-SNMP agents" section below), setup the agent as a service and run it using the command:

sudo  launchctl load -w /System/Library/LaunchDaemons/org.net-snmp.snmpd.plist

Typical snmpd.conf for Net-SNMP agents

If you run an SNMP agent on a unix machine (including MAC OS X), you are most likely runnning the net-snmp agent (www.net-snmp.org, an open-source proven full feature SNMP agent). This is the default SNMP agent for linux, FreeBSD, Solaris, MAC OSX and probably many more...
Here is a sample snmpd.conf that will ensure NetScanner can get the information it needs from your device. The following configuration will grant read-only access to the community "public".

# the community you are granting "read" access to. If you change it to something
# else, make sure you use the same community string in NetScanner:
rocommunity public

# all other settings are optional but highly recommended as it will improve your 
# "scanning experience".

# where your device is Located
syslocation Sebastien's lap

# Who owns or is in charge of the device
syscontact Sebastien

# Friendly display name for your device. (NetScanner displays this below the  
# device IP address in the scan result if it is configured).
sysName MacBookPro 

# the system object ID for this device. This is optional but highly recommended,
# it will help NetScanner identify the OS of the machine.  
# Replace 1.3.6.1.4.1.8072.3.2.16 with the appropriate entrye from 
# http://www.oidview.com/mibs/8072/NET-SNMP-TC.html
# For instance replace the 16 at the end by a 10 for linux.
sysobjectid 1.3.6.1.4.1.8072.3.2.16

Please note the default snmpd.conf files tend to be bloated with lots of unnecessary complex configuration in it. The reality is you don't need more that the few lines of text above. My suggestion is to backup your original file and start a new snmpd.conf from scratch using the template above.

Also don't forget on unix's, you need to restart the snmpd process for any changes to take effect. (sudo killall -9 snmpd should work on systems where the agent is correctly configured as a service, the system will restart the process after you kill it).

Enable SNMP on Juniper devices

Do you have a better link you think we should include? Please let us know freerangedevelopers@gmail.com.

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