The CUG index of the 'preferential CUG' for this address.
There can be only one 'preferential CUG' for an address.
A CUG user subscribing to 'preferential CUG' nominates a
CUG index which the network uses as a default to identify
the required CUG in the absence of any CUG information
in the outgoing call request.
A value of zero means the address does not have a
preferential CUG. The value of this variable must
correspond to a 'cwaCugIndex' of an entry in the
'cwaCugTable'. When an entry is created by the managed
system, this variable has a value of 0.
When selecting a 'preferential' CUG in the address's CUGs,
the corresponding CUG must allow outgoing calls.
This means 'cwaCallsBarred'(Outgoing Calls Barred)
must not have a value of outgoing(2) for the corresponding
CUG.