Configuring Inter-AS VPN Option B
If the MPLS VPN backbone network spans multiple ASs, inter-AS VPN is required. When the ASBRs do not have enough interfaces for all the inter-AS VPNs, inter-AS VPN Option B can be used.
Pre-configuration Tasks
Before configuring inter-AS VPN Option B, complete the following tasks:
- Configure an Interior Gateway Protocol (IGP) for the MPLS backbone network of each AS to ensure IP connectivity on the backbone network within each AS.
- Configure the basic MPLS functions and MPLS Label Distribution Protocol (LDP) for the MPLS backbone network of each AS.
- In each AS, configure VPN instances on the PE devices connected to CE devices and associate the VPN instances with PE interfaces connected to CE devices.
- Configure route exchange between the PE and CE devices in each AS.
For details about the configurations, see Configuring Basic BGP/MPLS IPv6 VPN.
Configuration Procedure
Controlling the Receiving and Sending of VPN Routes by Using Routing Policies and (Optional) Enabling Next-Hop-based Label Allocation on the ASBR are optional, and other tasks are mandatory. Perform these tasks in this sequence to complete inter-AS VPN Option B configuration.
When multiple tunnels need to perform load balancing to fully use network resources, you also need to complete the task of Configuring and Applying a Tunnel Policy.
In inter-AS VPN Option B, the ASBRs maintain and advertise VPNv4 routes of inter-AS VPNs, and they can also work as PE devices. When the ASBRs work as PE devices, configure VPN instances on the ASBRs to enable them to exchange routing information with CE devices. The configuration is the same as that on common PE devices.
The inter-AS VPN Option B scenario does not support TE tunnels.