Question

A service provider runs an MPLS L3VPN backbone. Two customers, CustA and CustB, both use the overlapping prefix 10.1.1.0/24 within their own VRFs on the same PE router. The provider configures both VRFs with the same route distinguisher (RD) 65000:100 but with different route targets. After the configuration, CustB's site cannot reach several of its own prefixes, and the PE's BGP VPNv4 table appears to show only one instance of 10.1.1.0/24. What is the root cause of this problem?

Accepted Answer

Both VRFs share the same RD, so the resulting VPNv4 prefixes are not unique and one overlapping route is discarded as a duplicate in the BGP table

Answer

The route targets differ between the VRFs, which prevents the PE from importing either prefix into the VPNv4 table

Answer

A single RD cannot be assigned to any VRF; RDs must be globally unique per PE regardless of overlapping prefixes

Answer

The MP-BGP session is not using the extended community attribute, so RD values are ignored during route advertisement