To reduce the number of MP-BGP VPN tunnels in a group of IP/MPLS PE routers that are part of the same L3 VPN instance, a hierarchy can be established by reexporting the VPN IP routes on a PE aggregation router (which can be an ABR node). In the case of VPRN service labels, reexporting VPN IP routes reduces the required MPLS FIB resources to the scale available on smaller access routers.
Use the config>service>vprn>allow-export-bgp-vpn command to configure the feature. This command enables the vrf-export and vrf-target export functions to include BGP-VPN routes that are installed in the VPRN route table.
When a route is installed in the VPRN route table, the route is exported as a new VPN-IP route to an MP-IBGP peer only; that is, the route is accepted by the VRF export policy but may be rejected by a BGP export policy. Assuming that the export policies have simple accept and reject actions, the new VPN-IP route is the same as the original VPN-IP route, except in the following cases.
The RD is changed to the value of the advertising VPRN.
The BGP next-hop is changed to a local address of the PE.
The label value is changed to the per-VRF label value of the advertising VPRN.