How to Implement the Snmpwalk Utility in Python

The SNMP (Simple Network Management Protocol) protocol is used in network management systems for communication between a server and a remote device. The server is called the manager, and the remote device is referred to as the agent.

The agent in the MIB creates all the information that a manager can read and control. The MIB is a table structure similar to a tree with numbers representing all nodes.

This protocol is not implemented natively by Python. In Python, we use the netsnmp module, an open-source module providing different tools for emulating various SNMP utilities.

This tutorial will demonstrate Python’s netsnmp module for the snmpwalk utility.

Implement the snmpwalk Utility in Python

We can retrieve SNMP management data using SNMP GETNEXT requests. The snmpwalk uses these GETNEXT requests to retrieve values from the MIB hierarchy.

With the snmpwalk application, we run multiple requests to get the values from the whole MIB hierarchy at once.

To implement in Python, we can use the netsnmp.snmpwalk() function to emulate the snmpwalk utility. It accepts a VarList or VarBind from which the snmpwalk will begin.

It returns the values from the MIB in a tuple. It is recommended to pass a VarList instead of a VarBind because a VarList is repeatedly updated till it contains the complete set of VarBind for the results.

If the VarBind is passed, it is impossible to examine the returned OIDs.

As shown below, we will use this function to emulate snmpwalk in Python.

import netsnmp

server = "172.xx.x.x"
password = "snmp_private"

oids_varlist = netsnmp.VarList("IF-MIB::ifName", "IF-MIB::ifDescr")
result = netsnmp.snmpwalk(oids_varlist, Version=2, DestHost=server, Community=password)

In the above example, we create a VarList using the netsnmp.VarList() constructor. This is passed with the server and password details of the manager in netsnmp.snmpwalk() to retrieve the network information.