Specifies how the forwarding function shall handle unicast
frames when it does not know what interface to use for
reaching a destination.
auto(1). Equivalent to `mac(2)' if the forwarding function
is connected to at least three interfaces, otherwise
equivalent to `nomac(3)'. If the device does not support
`mac(2)', then `auto(1)' is always equivalent to `nomac(3)'.
mac(2). The forwarding function will learn what interfaces
to use for a destination. This is done by looking at the
source MAC address on received frames. When the forwarding
function has learned what interface to use, it will forward
the frame on that interface only. Learning is also
specified for each interface and traffic class with
ethIfQueueLearning.
nomac(3). The forwarding function will forward the frame on
all its interfaces.