MPLS - VPNv4 Labels are assigned per route
In an MPLS environment where VPNv4 addresses are used, each route received by the PE router from a customer will be assigned a unique VPNv4 label. This ensures that the PE router is able to keep track of each individual route separately for forwarding purposes. This process is essential for maintaining the isolation between different VPNs on the same PE router.
Links:
https://forum.networklessons.com/t/mpls-layer-3-vpn-explained/1287/227?u=lagapidis