Question

An MPLS L3VPN service provider connects two sites of customer 'Acme' using eBGP as the PE-CE routing protocol. Both Acme sites use AS 65200. The provider PE routers redistribute customer routes into MP-BGP normally, and VPNv4 routes are exchanged between PEs with correct route targets. However, Site B never learns the prefixes originated at Site A. The PE at Site B shows the Site A prefixes in its BGP table but marks them as not received/denied by the CE. What is the most likely cause and fix?

Accepted Answer

The CE at Site B rejects the routes because its own AS (65200) appears in the AS_PATH; enable 'neighbor <ce> as-override' on the Site B PE.

Answer

The route target import/export values are mismatched between the two VRFs; correct the RT under the VRF configuration on both PEs.

Answer

The route distinguisher is identical on both PEs, causing the routes to be treated as duplicates; assign a unique RD per PE.

Answer

MP-BGP is not carrying the VPN label; enable 'send-label' under the vpnv4 address family on both PEs.