powerconnect blade switches and out-of-band interface

Hi,

We have a few PowerConnect M6220 and M8024 in an M1000e blade chassis.

Can anyone explain the concept of the out-of-band interface?

What are the differences with the management interface?

Also, it appears that if we assign an IP address to the management interface, we have to shutdown the out-of-band interface, to be able to access the switch on the management interface: if we don't shut it down, it appears the switch will try to route management traffic through the out-of-band interface.

Is that the expected behavior?

Thanks.