Description: This object is used to set the mode in which default routes are advertised: null(0): indicates that default routes are not advertised. always(1): indicates that default routes are always advertised. matchdefault(2): If there is the default route that is generated by another routing protocol or another IS-IS process in the routing table, this default route is advertised in an LSP. If this default route is deleted from the routing table, this default route is not advertised in the LSP. routepolicy(3): indicates that default routes are advertised according to the routing policy.