Router Virtualization

Was trying to find out how one can virtualize the cisco router in ESX.
Have a look at this for some motivation behind this.
The following methods are possible today:

1. Create a virtual Linux box and run Quagga or XORP on it.
2. http://www.thevarguy.com/2012/07/23/vmware-nicira-vs-cisco-insieme-virtualized-network-war/
3. Can Openflow be of relevance [see this], and this

Investigating this further. Let me try to find out what is a good solution.