Advanced VRF Import and Export Features

Selective VRF Import

    Selective route import uses a route map that can filter the routes selected by the RT import filter.
        The routes imported into a VRF are BGP routes, so you can use match conditions in a route map to match any BGP attribute of a route.
        The import route map is deployed in the receiving VRF.
        A route has to pass the RT import filter first and then the import route map.
        First, at least one of the RTs attached to the route needs to match one of the import RTs configured in the VRF.
        Second, the route is permitted by the import route map.
    import map route-map-name attaches a route map to the VRF import process.
        A route is imported into the VRF only if at least one RT attached to the route matches one RT configured in the VRF AND the route is accepted by the route map.



Selective VRF Export

    Some advanced MPLS VPN topologies are easiest to implement if you can attach a variety of RTs to routes exported from the same VRF.
        This capability allows only a subset of the routes exported from a VRF to be imported into another VRF.
        The export route map is deployed in the originating VRF.
       A route map can be specified for each VRF to attach additional RTs to routes exported from that VRF.
        The export route map performs only the attachment of RT's. It does not perform any filtering function.
    Attributes attached to a route with an export route map are combined with the export RT attributes.
        If you specify export RTs in a VRF and set RTs with an export route map, all specified RTs will be attached to the exported route.
    set extcommunity rt extended-community-value [additive] sets the BGP extended community attribute for a RT.
    export map route-map-name attaches a route map to the VRF export process.

Copied from:  http://mynetworkingwiki.com/index.php/Advanced_VRF_Import_and_Export_Features