Configuring the Carrier's Carrier (Solution 1)

Usage Scenario

If a BGP/MPLS IP VPN user is a service provider, who offers BGP/MPLS IP VPN services to its clients, the function of carrier's carrier can be applied. Compared with a basic BGP/MPLS IP VPN, the access of provider carrier CEs to provider carrier PEs is the key to the carrier's carrier model. Table 1 shows the implementation scheme of the carrier.

**Table 1** Carrier's carrier solution
Solution	Solution between the Level 1 carrier PE and Level 1 carrier CE	Solution Between the Level 2 Carrier PE and the Level 1 Carrier CE
Solution 1	IGP and LDP multi-instance are used to exchange routing information.	Use IGP and LDP to exchange routing information.
Solution 2	Use EBGP to exchange labeled IPv4 VPN routes.	BGP label distribution solution: Establish IBGP peer relationships to establish complete public network tunnels between the PEs of the Level 2 carrier.
Solution 2	Use EBGP to exchange labeled IPv4 VPN routes.	LDP label distribution for BGP: No IBGP peer relationship is established. After the Level 2 carrier learns the labeled BGP routes of the public network from the Level 1 carrier's devices, the Level 2 carrier imports the BGP routes to the IGP protocol and triggers LDP to distribute labels for these routes. In this manner, a complete LDP LSP can be established between the PEs of the Level 2 carrier.

This section describes solution 1, that is, the LDP multi-instance solution.

Pre-configuration Tasks

Before configuring the carrier's carrier, complete the following tasks:

Configure an IGP for the Level 1 carrier's MPLS backbone network to implement the IP connectivity of the backbone network.
Configure basic MPLS functions and MPLS LDP for the Level 1 carrier's MPLS backbone network.
Establish an MP-IBGP connection between the Level 1 carrier PEs.
Configure an IGP for the Level 2 carrier's IP network or MPLS network to implement IP connectivity.
Configure basic MPLS functions and LDP on the Level 2 carrier network and set up LSPs.

Configuring the Level 1 Carrier CE to Access the Level 1 Carrier PE (Using LDP Multi-Instance): When the Level 1 carrier and Level 2 carrier are in the same AS, the Level 1 carrier takes the Level 2 carrier as its VPN user.

Configuring a Level 2 Carrier CE to Access a Level 2 Carrier PE: In the Level 2 carrier networking, for the CE's access to a PE, you need to create a VPN instance on the Level 2 PE and configure a routing protocol between the PE and CE, the configuration of which is similar to the configuration in the basic BGP/MPLS IP VPN.

Configuring the External Route Exchange Between Level 2 Carrier PEs: An MP-BGP peer relationship is established between Level 2 carrier PEs to exchange IPv4 VPN routes.

Verifying the Configuration: After carrier's carrier is configured, you can check information about public network routes and VPN routes on PEs and CEs of the Level 2 carrier and Level 1 carrier.