Use the following in expert mode to disable gateway via data interfaces:
vi /etc/sysconfig/network-scripts/ifcfg-internal-route and changed the INTERNAL_ROUTE_ENABLED=1 to INTERNAL_ROUTE_ENABLED=0
Exit Expert mode. Then issue a configure network ipv4 manual 1.1.1.2 255.255.255.0 1.1.1.1 to reconfigure the management IP.
The show network command now shows the gateway.
