Joe Switch writes in to ask what the deal is with Virtual Routers and other such untangable networks. Matt has the answer. The way I understand it your more high end (read: expensive) Cisco and Juniper routers have virtual routers built in -- much like you might have a virtual interface like eth0:1 in Linux -- to manage VLANS, IP subnets and such.

Matt goes on to explain that in the vSphere product by VMware you can use the APIs to write, basically, a software based switch to compliment your existing deployments. Check out the Cisco Nexus 1000V. It's a software implementation of a Cisco Nexus switch. I'd love to get my hands on it but at nearly $1000/year I'll find something open source. Speaking of which, we've been meaning to play with a Cisco virtual network application but are in need of an ISO. If you're privy to an open source alternative or can help out drop us a line.