Understanding Selective VRF Import for MPLS VPN Managed Services

D.

Selective VRF import is an advanced VPN feature in which only specific prefixes are present in the required VPNs. When using this feature, the MPLS engineering team needs to consider several aspects.

Option A states that a route must pass the import route map first and then the route target import filter. This is correct. The import route map is used to filter the prefixes that are imported into the VRF, and the route target import filter is used to match the route targets of the prefixes that are imported. Therefore, a route must pass the import route map first before it is checked against the route target import filter.

Option B states that the routers that are imported in the VRF can be BGP and IGP routes, so other match conditions in the route map, besides communities, can be used. This is also correct. The route map can use other match conditions besides communities to filter the prefixes that are imported into the VRF. For example, it can use prefix lists or access lists to filter prefixes.

Option C states that the import-map command is applied under the PE interface that connects to the CE router. This is incorrect. The import-map command is used to specify the import route map that is used to filter prefixes that are imported into the VRF. It is applied in the VRF configuration mode.

Option D states that a route is imported into the VRF only when at least one RT that is attached to the route matches one RT that is configured in the VRF and the route is permitted by the import route map. This is also correct. The route targets of the prefixes that are imported into the VRF must match the route targets that are configured in the VRF, and the prefixes must also be permitted by the import route map.

In summary, the MPLS engineering team must consider the following aspects when using the selective VRF import feature:

• A route must pass the import route map first and then the route target import filter.
• The route map can use other match conditions besides communities to filter the prefixes that are imported into the VRF.
• The import-map command is applied in the VRF configuration mode.
• The route targets of the prefixes that are imported into the VRF must match the route targets that are configured in the VRF, and the prefixes must also be permitted by the import route map.