Configuring the Carrier's Carrier in an Independent Label Address Family (LDP Label Distribution for BGP)

After LDP LSPs are established for labeled BGP routes of the public network, IBGP peer relationships do not need to be established within the Level 2 carrier network, and the Level 2 carrier can provide BGP/MPLS IP VPN services. This section describes how to use a separate labeled address family (BGP-labeled address family or BGP-labeled-VPN instance IPv4 address family) to configure inter-AS BGP LSPs. This configuration implements the carrier's carrier function.

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.

Two solutions can be adopted to realize carrier's carrier:

BGP label distribution: An IBGP peer relationship is established between a Level 1 carrier CE and a Level 2 carrier PE to establish a complete public network tunnel between the Level 2 carrier PEs.
LDP label distribution for BGP: No IBGP peer relationship is established between a Level 1 carrier CE and a Level 2 carrier PE. After learning labeled BGP routes of the public network from the Level 1 carrier, the Level 2 carrier can import these BGP routes to the IGP routing table and use LDP to distribute labels for these routes. In this manner, a complete LDP LSP can be established between Level 2 carrier PEs.

This section describes how LDP distributes labels for BGP. In this solution, a BGP peer relationship is established in a BGP-labeled address family or BGP-labeled-VPN instance IPv4 address family so that the BGP peers can advertise BGP-labeled routes to each other, allowing BGP LSPs to be set up between the BGP peers.

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 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 MPLS LDP for the network of the Level 2 carrier and establish LSPs if the Level 2 carrier provides BGP/MPLS IP VPN service.

Configuring a Level 1 Carrier CE to Access Level 1 Carrier PEs: When Level 1 and Level 2 carriers are in different ASs, the Level 2 carrier functions as the VPN user of the Level 1 carrier, the scenario of which is the same as that the CE's access to the PE in the basic BGP/MPLS IP VPN.

Configuring the Level 2 Carrier's Clients to Access the Level 2 Carrier's 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 External Route Exchanges Between Level 2 Carrier PEs: The MP-BGP peer relationship is established between PEs of the Level 2 carrier to exchange IPv4 VPN routes.

Importing BGP routes to the IGP Routing Table: To enable LDP to allocate labels for BGP, you need first import BGP routes to the relevant IGP routing table.

Configuring LDP to Distribute Labels for the Labeled BGP Routes of the Public Network: By allocating labels for labeled BGP routes, you can establish LDP LSPs for labeled BGP routes in the Level 2 carrier' network.

Verifying the Configuration of Carrier's Carrier in an Independent Labeled Address Family (Solution 2): After configuring carrier's carrier, you can view information about public network routes on PEs and CEs of carriers at different levels, VPN routes on the PEs, and LDP LSPs.