We host applications such as Exchange email for some of our clients. 100% up-time is very crucial for most of these clients. We have two datacenters with a VPN between them. My Server guys are working on a WMWare High Availability solution between the datacenters. As far as routing is concerned I am little confused. I'm thinking I will need a BGP solution for this to work from what I'm reading. Let's say mail.domain.com in located in datacenter 1, if the internet fails or the exchange servers fails, our plan is for it to failover ot datacenter 2. So right now mail.domain.com in DNS has an IP in Datacenter 1 IP Block. Data Center 2 has a totally different IP Block, so how will mail be routed to Datacenter 2. Each location has a Cisco 2851 as the WAN Router along with a Cisco ASA5520 behind it for firewall and VPN. If anyone can shed some light on this I would greatly appreciate it.