The IP address of the interface used for this neighbor. If
this value is set to zero OSPF will choose a suitable interface
to use. If this value is non-zero this neighbor will only be
associated with an exactly matching interface.
Note this field is only used for NBMA and P2MP links. Also,
the etsysOspfExtNbrAdminStatus object must be 'disabled' prior
to modifiying this object.