After LDP LSPs are established for the labeled BGP routes
of the public network, EBGP connections in multi-hop mode are established
between PEs of different ASs to exchange VPNv4 routes.
After the routes of the loopback interface on a PE in an AS are advertised to the remote PE in another AS, the MP-EBGP peer relationship is established between the PEs.
By enabling LDP on ASBRs to allocate labels for BGP, you can establish LDP LSPs for labeled BGP routes of the public network that are filtered in the IP prefix list
By introducing extended community attributes to BGP, MP-IBGP can advertise VPNv4 routes between PEs. PEs of different ASs are generally not directly connected. Therefore, to set up the EBGP connection between the PEs of different ASs, configure the permitted maximum hops between the PEs.