We are consolidating multiple regional data centers into a single data center (Hosted vSphere). The requirements are that the new data center keeps the same IP addressing schema as they used to have. At the same time they can't decide how they will cut over to the new data center (Cold Cut or gradual migration) In my opinion they need to decide which method they will use as this will alter the Network design at every level..
Please don't ask me why the decision makers are insisting on this I have already fought a political battle about how outrageously stupid this request is and how the Network is not a magical unicorn that can sparkle all the issues away. I still cant get my head around how to allow the same IP subnet to sit in 2 connected routable L3 Networks without doing some NAT voodoo and Host routes.
Their justifications is that they don’t want to have to change any Hard coded IP addresses in the Applications but they are not even sure if there are any hard coded IP's in the first place. They rely on an external vendor to manage this for them and any time you ask them for anything they charge an extortionate amount of money even to look into anything.
So my question is.. Have any of you come across this kind of lunacy and do you have any advice or knowledge about how to approach this migration?
I can't see how both the current IP addressing/DNS scheme can live at 2 physical locations at once without massive L3 issues.
After searching high and low I want to avoid NAT since we don’t know if the applications can live with that. I think possible "Stretching the VLAN" may be a good option that way we can gradually migrate the VM's across and we will not be forced to do a cold cut
All thoughts welcome !