The value of vRtrPimNgAFGenMdtDefGrpAddress specifies the default
core group address of the Multicast Distribution Tree(MDT)
for the VPRN instance.
All the customer PIM control is sent in the service provider network
using the default group address. Customer data traffic for which
a Data MDT is not used is also sent on the default tunnel. The
Multicast Tunnel(MT) interface for a VPRN is created when this object
is set to a valid group address. The MT interface is deleted when the
object is reset to its default value.
The value of this object is not applicable when the value of
vRtrPimNgAFGenMvpnGrpAddrMode is set to 'none'.