Virtualization in the Network Designer’s Toolbox

by Jeff Loughridge

I’ve found virtualization increasingly useful in my work. I thought I’d share my observations on effectively using virtualization for feature testing, architecture validation, and learning. Virtualization is a very inexpensive way to accomplish tasks that previously required thousands of dollars in lab equipment.

The first decision in employing virtualization is selection where to establish your test environment. The advantage of using a dedicated server is that your applications aren’t competing for resources with the test environment. You can get a server with a lot of memory, which I would advise if you plan on using many virtual machines simultaneously. I prefer Ubuntu Server LTS for headless servers. Ubuntu provides a very stable host OS.

An alternative is creating the virtual environment on your laptop. This comes in very handy if you find yourself without Internet connectivity or you deliver a demo to customers. If you are at a customer site, do not expect to be able to reach your server. There are too many problems that can arise. For my needs, I maintain virtualized labs on both my laptop and office server.

For software, I recommend purchasing VMware Workstation 7.1. VirtualBox has its uses; however, Workstation is a better option. It has features not available in VirtualBox. Let’s take a look.

  • Teaming – Workstation lets you set up a group of VMs in a way that makes it easier to manage the virtual infrastructure. You do things such as start and stop all the VMs in the team. Over time, you end having numerous VMs for different purposes. The ability to group VMs into teams is a convenience.
  • VM Recording/Playback – This is an excellent feature for creating demos.
  • Virtual Network Editor – Creating the virtual network infrastructure is very simple in Workstation. When you combine teaming with the virtual network editor, you can set up new labs very quickly.
VMware Workstation has additional benefits. For those new to virtualization, the software introduces you to concepts and terminology that VMware uses across its product family. I use Workstation for one of the same reasons I use Ubuntu. When something breaks, you can almost inevitably find someone else who has encountered the problem by doing a web search. Don’t expect this if you use VirtualBox. Don’t get me wrong– I’m a proponent of open source software. In this case, the better product is clearly Workstation. On a related note, avoid qemu and its derivatives like the plague. Setting up bridging by hand and figuring out poorly documented command line flags is a hassle you don’t need.


Be very wary about connecting a virtualized environment to the old Cisco router you have in storage. I’ve made the mistake of trying to connect VMs and tangible networks. For performing testing, do this as a last resort. You don’t want to spend time when something breaks figuring out if the problem lies in the interconnection of physical and virtual gear.


To give you an idea of how I use virtualization, I’ll share several items on my to-do list. (Can you guess that I’m thinking about IPv6 a lot these days?)
  • Ecdysis NAT64/DNS64 – While I wouldn’t recommend beta software to clients, I don’t have commercial NAT64/DNS64 products in my lab. I want to investigate the IPv6-only user experience across various OSes.
  • Linux installation with IPv6-only connectivity– After doing some basic testing, I suspect that the developers of some distributions assume that end stations are dual stack. For example, I’ve been unable to get CentOS to install with only IPv6 connectivity. The installer sends DNS queries for A records only. I hope to write a report on the state of IPv6-only installations across the major distributions prior to end of year.
  • IPv6 Router Advertisement Option for DNS Configuration (RFC5006) – Recently there has been discussion on the v6ops list about replicating functionality in both DHCPv6 and SLAAC.  As a core guy, I haven’t worked extensively DHCPv6. I’d like to see DNS server assignment as explained in RFC5006. I believe only Linux supports the RFC. I’ll confirm.
If you are like most engineers, you enjoy taking things apart and understanding the details of how they work. Virtualization gives you the ability to do this without a big investment. Go forth and virtualize.

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