Just an update on this - for cDOT 8.3. I had some issues finding the correct command with NetApp documentation. You can change the e0M network interface IP/subnet with the following command (Run this from console connection)
CLUSTER::> network interface show -curr-port e0M
displays entries that can be modified for the e0M management port for proper command syntax
CLUSTER::> set advance
advance command structure - approve
CLUSTER::> network interface modify -vserver -lif LIFNAME -home-node HOMENODE -home-port e0M -address IPADDRESS -netmask NETMASK
you may have to include -force-subnet-assocation
The subnet should be created prior to moving IPs from my experience.