IP Fragmentation Lab with Vagrant

Recently, I had a need to understand IP fragmentation better, so I built a lab to experiment with.  I wanted it to be easy to setup, and built in a way that is repeatable by others, so I designed automation to stand it up with virtual machines in a hypervisor. The lab network topology is shown in Figure 1.


Figure 1 – Network Diagram for IP Fragmentation Lab

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NetFlow on OpenWRT

This blog post is for network experimenters who want to export flow records from a small network, such as a home network using an OpenWRT router. Such a network might look like this:


Flow records can be useful for various applications. Here is an example flow record:

Date first seen          Duration Proto      Src IP Addr:Port          Dst IP Addr:Port   Packets    Bytes Flows

2018-08-04 21:31:34.518     0.000 TCP ->            100     4600     1

Flow records give a coarse-grained view of what traffic is passing over a network, including flow source and destination addresses/protocols/ports, as well as volume information such as packets and bytes.

In this tutorial we use OpenWRT[1], a popular free and open source router operating system, and add the softflowd package to it to generate NetFlow flow records. There are however many other options to achieve the same outcome. Continue reading

Vagrant for SDN Labs

Part 1 – Introduction

I’ve been experimenting with Vagrant to automate the creation of virtual Software-Defined Networking (SDN) labs. This blog explains how create SDN labs with Vagrant.

Why SDN labs? Maybe you’re a network student or engineer learning new skills. Maybe you want to develop the next killer SDN app. Perhaps you’re doing SDN research. Virtual labs are a great way to test ideas without having to invest in SDN switch hardware, and can be set up quickly. Continue reading

Build a Home SDN Lab

Software-defined networking (SDN) separates network control from packet forwarding. SDN is great for experimenters, as we get to tinker with how the network runs, without having to worry about moving packets.

To play with SDN in your home network you’ll need a device to do the packet forwarding, under control of your software.

I’ve added instructions on how to build a home SDN lab that leverages a common consumer-grade TP-Link home router repurposed as an OpenFlow switch, including Wi-Fi.

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