A device module is a piece of hardware containing several device interfaces. For example, a HWIC-4ESW module contains four Ethernet (10 MBps) ports. Similar to a real router/switch, the device has to be powered off in order to add or remove modules.

The power switch is on the right-hand side of each device, with a green LED indicating that the power is on. Click on this switch to turn it off. To add a module, drag one from the modules list and drop it onto an empty slot. If a module doesn't fit into that slot, it automatically returns to the module list.

To remove a module, power off the device and drag it from the slot back to the module list.