MPLS Local Label Allocation Filtering
In an MPLS network, the mpls ldp label command enables a feature called local label allocation filtering, which selectively allocates local labels for a subset of the prefixes learned from the IGP. The purpose of this command is to keep the size of the local label space low, as well as to limit the number of advertisements to peers. This in turn increases the scalability for especially large networks.
This is in contrast to MPLS LDP Label Filtering using the mpls ldp advertise-labels command, which does not change the local label allocation but changes the advertisement process.
Links
https://forum.networklessons.com/t/mpls-ldp-label-filtering-example/1016/30?u=lagapides
https://networklessons.com/mpls/mpls-ldp-label-filtering-example/