We are about to build a New Data centre to eventually replace one of two current data centres. The project manager has decided they would like to use the same address range for the new data centre as the current data centre so servers can be easily moved in stages with minimal config changes. The data centre that is being replaced is only small and has one VLAN.
Each of our servers use dual nics with the default gateway set to the HSRP address of the VLAN.
The current two data centres are connected over an etherchannel which we route across.
The only way I can think of doing this is to have a trunk between the three data centres. When servers are moved from the old data centre to the new data centre their DG would remain unchanged. (HSRP address of VLAN at the old data centre)
To me this just doesn't seem good practice. Can anyone see a any potential issues with this. I need to put up a good argument to have a new address range for the new data centre.
Any help much appreciated.