The IP subsystem fallover behavior of a two-node cluster is being testing in a large client organization. One of the tests is to simulate a network_down event and verify that HACMP movesthe single resource group to the standby node. What is the best way to simulate a network down condition？（）
- A Turn off the IP core switch connecting the two nodes.
- B Issue the command "stopsrc -g inetd" on the node that has the resource group.
- C Issue the command "sh /etc/rc.tcpclean" on the node that has the resource group.
- D Simultaneously unplug all network cables from the node that has the resource group.