Snimpy: interactive SNMP tool

Snimpy is a Python-based tool providing a simple interface to build SNMP query. Here is a very simplistic example that allows us to display the routing table of a given host:

m=M("localhost", "public", 2)
routes = m.ipCidrRouteNextHop
for x in routes:
    net, netmask, tos, src = x
    print("%15s/%-15s via %-15s src %-15s" % (net, netmask, routes[x], src))

You can either use Snimpy interactively throught its console (derived from Python own console or from IPython if available) or write Snimpy scripts which are just Python scripts with some global variables available.

Why another tool?

There are a lot of SNMP tools available but most of them have important drawback when you need to reliably automatize operations.

snmpget, snmpset and snmpwalk are difficult to use in scripts. Errors are printed on standard output and there is no easy way to tell if the command was successful or not. Moreover, results can be multiline (a long HexString for example). At least, automatisation is done through the shell and OID or bit manipulation are quite difficult.

Net-SNMP provides officiel bindings for Perl and Python. Unfortunately, the integration is quite poor. You don’t have an easy way to load and browse MIBs and error handling is inexistant. For example, the Python bindings will return None for a non-existant OID. Having to check for this on each request is quite cumbersome.

For Python, there are other bindings. For example, pysnmp provides a pure Python implementation. However, MIBs need to be compiled. Moreover, the exposed interface is still low-level. Sending a simple SNMP GET can either take 10 lines or one line wrapped into 10 lines.

The two main points of Snimpy are:

  • very high-level interface relying on MIBs
  • raise exceptions when something goes wrong

Meantime, another Pythonic SNMP library based on Net-SNMP has been released: Easy SNMP. Its interface is a less Pythonic than Snimpy but it doesn’t need MIBs to work.