By default on cisco router labels are generated for each and every route. So when you use the command “mpls ldp advertise-label” it means it will advertise all the labels to its adjacent neighbours. But in actual neighbours require only the labels for loopbacks which are being used for MP-BGP. So there is no requirement to advertise all the labels. For saving the overhead we can advertise the labels only for the loopback addresses by using an acl “mpls ldp advertise-label for mpls_acl”.