MPLS LDP (Label Distribution Protocol)

Hi Stuart,

Did you see this tutorial?

https://networklessons.com/mpls/mpls-layer-3-vpn-explained/

I think that one will be helpful to understand this better. Within the MPLS “core”, we only advertise the loopback interfaces of the PE routers in our IGP, OSPF in most of my examples. The P router will only have these networks in its routing table. The LIB is based on the information of the RIB (Routing Table), so you only find labels for those loopbacks there, these are the transport labels needed to get from one PE to another PE.

Only the PE routers have to know all customer routes, these (including a VPN label) are advertised through IBGP between the PE routers.

Keep in mind that the LIB is built based on information from the RIB. If there are multiple paths to a certain PE router, then your IGP will decide which path will be installed in the RIB, which results what is used in the LIB. This is something we can influence with MPLS traffic engineering though.