Automatic network discovery and documentation


NetBrain is a famous software that allows network discovery (and management). Let's focus now on network discovery and documentation: we want to automatically discover network devices, how they're connected, and store everything into a version control repository (GIT/CVS).

So we want to:

  • discover all network devices;
  • map how they’re connected together;
  • track changes automatically;
  • store everything into a version control repository (GIT/CVS);
  • visualize any updated map with a simple browser.

How we can solve the above problem:

  • we assume all devices by Cisco, so we can use CDP;
  • we can get CDP data via SNMPv3;
  • we can build a (source, destination) topology;
  • we can store the topology into a revision control repository (GIT/CVS);
  • we can use jsPlumb to render the (source, destination) topology into a web page.


netdoc is the small experiment I wrote to solve the problem. It contains two Python scripts:

  • to discover network devices via SNMPv3 and generates two .ini files:
    • discovered_nodes.ini: contains all network devices with some additional information
    • discovered_connections.ini: contains all network connections with some additional information
  • to plot a web page from the above .ini files.

.ini files can be stored into a revision control repository.

Running netconf

Currently netdoc is a POC script, so maybe it can work on your infrastructure, maybe it won’t. To start it, run:

# ./ -u snmpv3user -p snmpv3password -h -h -h

The discovered_nodes.ini file contains all CDP discovered devices in the following form:

id = AccessServer
image = router.svg
disabled = false
platform = cisco 2610

The title is the CDP neighbor ID (usually the hostname); other attributes are:

  • id: the CDP neighbor ID (usually the hostname)
  • image: an image used to display the node in the web page
  • disabled: true if missing during last scan
  • platform: the CDP neighbor platform

The discovered_connections.ini file contains all CDP discovered connections in the following form:

source = AccessServer
source_if = e0/0
destination =
destination_if = gi2/0/46
disabled = false

The title is the source and destination CDP neighbor ID with interface names; other attributes are:

  • source: the source CDP neighbor ID
  • source_if: the source interface name
  • destination: the destination CDP neighbor ID
  • destination_id: the destination interface name
  • disabled: true if missing during last scan

After a successful scan we can create the html page:

# ./ > netdoc.html

And here we go, a draggable web page:

netdoc image map


Posted on 28 Mar 2017.
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