Brocade has a beta exam up for BCVRE - Certified vRouter Engineer - which is on the Vyatta software from the company with the same name that Brocade bought last year.
There is the free open source core. Download from here: http://vyatta.org/downloads (no you don't have to register). The evaluation/subscriber version has the API and web gui available, I'll probably check those out closer to the exam date.
I grabbed VC6.6 - Virtualization ISO. Use it in a VM and assign 5GB disk (install only requires 1G, or you could just run it on the iso, but then it doesn't keep state between reboots) and 1GB RAM. Two NICs: One NAT and one private. But to get more acquainted with it you'll likely have to do a bit more configuration on the hypervisor side. Such as turn off dhcpd in your virtual networks.
To install it to disk: hit "install system" at the CLI after it's booted.
More documentation: http://docs.vyatta.com/current/wwhelp/wwhimpl/js/html/wwhelp.htm - there are descriptions how to get for example ssh management working ( set service ssh ).
The server is basically Debian with a more recent kernel (6.6 has 3.3) and a shell to make it more switch-like. It actually uses the bash completion to make it look like this. Check out /etc/bash_completion.d/vyatta-*
To remove a setting use "delete" (comparable to no in other CLIs). There is a web interface, but this is only for subscribers. Core version allows SNMP though if you want to use that :)
- VPN (for example connect private cloud <-> Amazon VPN)
- Routing (OSPF, BGP, etc)
But no SDN stuff (separate data and the control plane). It looks like it's not possible to modify the flow table of a switch via Vyatta. This looks like a software router/VPN/firewall with some extras added to it.