Hi llittlefield,  The default Subnets allocated to the internals of the VMAX3 are for EMC to access via ESRS. As with VMAX3 the new Module "VM" internals need a network to be contactable. To protect EMC and the customer the subnets need to be kept separate. By connecting the VMAX to the same subnet of the customers network. From the SP EMC would have open access to the customer and the customer to the VMAX Frame. This is something that is not in EMC or the customers best interest. 
Hi All,  A customer of mine is getting a new VMAX 250F. The customer has told me that they are using the 172.16.0.0, 172.17.0.0 and 172.18.0.0 in their datacenters already. These subnets are the default IP subnets used in the VMAX. As per the VMAX 250F installation documentation, we now have to request new IP subnets and perform the override procedure during the installation process.  The customer has asked why we have to change the default internal VMAX subnets?  If these are internal subnets, they should not be able to communicate out to the customer network.   So does anyone know why we have to change the default internal VMAX subnets?  Thank you,  Luke Littlefield
VMAX 250F - Question about the Internal default IP Subnets