I am planning networking equipment for a DR site that will be connected via a metro Ethernet connection. My primary site setup has a Cisco ASA router between the ISP and my Layer 3 core switch. All of my Layer 2 edge switches (representing different VLans) connect to my Layer 3 core switch through a 10gb backbone. I would assume that because of the Metro Ethernet connection I can connect the DR site as just another Layer 2 edge switch. In the event of a disaster (one that destroys my main site and network) I will be running all of my VM's from the DR site. The DR site will have a similar setup with a Cisco ASA connected to my ISP and users will be VPN'ing through the ASA to access the VM's.
If I lose the connection to the main campus, do I need a Layer 3 switch at the DR site or will a Layer 2 do the trick? I'm thinking that the DR Layer 2 switch would need to have the VLans required for the servers (both the physical hosts and the VM's) and the VLans required for the Internet traffic to/from the ISP. Would all of my traffic be able to get to where it needs to go? Can I configure the default route on the switch to go to the ASA?