image shows a group of people gathered together with a medium-sized telescope at sunset, used as a metaphor for network discovery

A key aspect of mapping the network is the ability to automatically discover the entire topology! This is so crucial that, in fact, at least half of the requests we get from our customers involve what we call ‘Layer 2 Discovery’.

It’s called Layer 2 (you can click here to read more about it on Wikipedia) because of the position in the OSI stack — Layer 3 is the IP layer which, while useful, doesn’t give you a complete picture of how the devices in your network are physically connected with each other as Layer 3 topology only provides the end-to-end routing connectivity for which the so-called edge-to-edge connections are, in many cases, transparent.

Customers need edge-to-edge (or Layer 2) connectivity: this provides a more accurate approximation of how devices are wired in the network. When we’re talking about physical connections, however, Layer 2 alone doesn’t give you a full picture either as you could have patch panels or dumb devices that can’t be discovered but are connected in between.
Layer 2 discovery does, however, give you a much closer approximation because it provides information about the edge-to-edge connectivity in your network (mentioned above). This edge-to-edge connectivity not only includes routers, but also switches and any devices that have a MAC address and a discovery protocol enabled (such as SNMP).

Discovery requirements

What are the basic discovery requirements?

The first requirement is obvious: you need the ability to discover the devices themselves in order to create a Layer 2 topology.

To discover devices,netTerrain currently employs different flavors of SNMP and other protocols. The netTerrain Collector, (which is a multi-tenant, distributed client) can be installed across multiple different networks and sends the discovered data to the netTerrain server in real-time, over a LAN or the Internet — or, if you work off-line: asynchronously. It’s important to note that netTerrain’s discovery process does not use agents.

The other requirement for a full topology discovery and network mapping is that the devices must expose the topology in some way via SNMP.

Current approach

Up until the forthcoming version 9, netTerrain has been using what could be described as more basic Layer 2 discovery features. Specifically, for topology discovery and link creation, we have been using MIB bridge tables, ping and…that’s about it.

A huge development coming up, and the reason for writing this blog, is this: we are now introducing CDP and LLDP as additional protocols to enhance netTerrain’s automated IT network mapping capabilities. We are also combining this with ARP tables so that we can produce a complete Layer 2 topology.

CDP and LLDP will rely on something called ‘seed discovery’: this means that in order to start a discovery the process begins with one specific IP address; the Collector then starts crawling the network to produce the complete map of your devices and IT infrastructure. So, in a sense, we are getting two features in one: both an improved Layer 2 topology and seed discovery.

This is all nice and dandy, but, before we get too excited about this, I have to remind the reader that this is still an upcoming feature, not yet available. To be fair, Version 8.6, which will be announced very soon, contains additional improvements — but the more hardcore Layer 2 topology discovery improvements mentioned here are currently under development and slated to come out later this year.

In sum, with its existing mapping capabilities plus CDP and LLDP, the netTerrain Collector will become the first fully cloud-enabled solution to automatically produce a network map via SNMP. We hope that with these improvements we can get closer to what we sometimes like to call ‘the magic red button’ (click here to read more on it), or, in other words, the holy grail: just press discover and voila!

About Jan Durnhofer

As CEO / Product and Engineering Manager, Jan joined Graphical Networks with the purpose of creating the most advanced DCIM and IT visualization company in the market.