Configuring Inter-AS VPN Option B
If virtual private network (VPN) routes need to be established over a Multiprotocol Label Switching (MPLS) backbone network spanning multiple autonomous areas (ASs), inter-AS VPN is required. If the provider edge (PE) devices connect to many VPNs but the autonomous area border routers (ASBRs) do not have enough interfaces to reserve an interface for each inter-AS VPN, the inter-AS VPN Option B solution can be used on the network.
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) or Resource Reservation Protocol-Traffic Engineering (RSVP-TE) 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 IP VPN Functions.
Configuration Procedure
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 configure tunnel policies. For details, see Configuring Tunnel Policies.
- 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.