A digital subscriber line (DSL) network provides enhanced dynamic spectrum management (DSM) based on estimated foreign interference obtained from monitoring unmanaged wire pairs in a cable. A DSL access multiplexer (DSLAM) or other line terminal provides vectored DSL signaling to a plurality of subscribers via a first set of wire pairs of the cable. The DSLAM monitors a second set of one or more wire pairs of the cable that are not connected to the vectored group associated with the first set of wire pairs to estimate foreign interference introduced to the first set of wire pairs. The DSLAM then modifies the vectored DSL transmitted signaling responsive to the estimated foreign interference so as to pre-cancel or otherwise compensate for the foreign interference introduced into the managed wire pairs.