Configuring VRF Route Targets for Routing Instances for an MBGP MVPN
By default, the VPN routing and forwarding (VRF) import and export route targets (configured either using VRF import and export policies or using the vrf-target statement) are used for importing and exporting routes with the MBGP MVPN network layer reachability information (NLRI).
You can use the export-target and import-target statements to override the default VRF import and export route targets. Export and import targets can also be specified specifically for sender sites or receiver sites, or can be borrowed from a configured unicast route target. Note that a sender site export route target is always advertised when security association routes are exported.
When you configure an MBGP MVPN routing instance, you should not configure a target value for an MBGP MVPN specific route target that is identical to a target value for a unicast route target configured in another routing instance.
Specifying route targets in the MBGP MVPN NLRI for sender and receiver sites is useful when there is a mix of sender only, receiver only, and sender and receiver sites. A sender site route target is used for exporting automatic discovery routes by a sender site and for importing automatic discovery routes by a receiver site. A receiver site route target is used for exporting routes by a receiver site and importing routes by a sender site. A sender and receiver site exports and imports routes with both route targets.
A provider edge (PE) router with sites in a specific MBGP MVPN must determine whether a received automatic discovery route is from a sender site or receiver site based on the following:
If the PE router is configured to be only in a sender site, route targets are imported only from receiver sites. Imported automatic discovery routes must be from a receiver site.
If the PE router is configured to be only in a receiver site, route targets are imported only from sender sites. Imported automatic discovery routes must be from a sender site.
If a PE router is configured to be in both sender sites and receiver sites, these guidelines apply:
Along with an import route target, you can optionally configure whether the route target is from a receiver or a sender site.
If a configuration is not provided, an imported automatic discovery route is treated as belonging to both the sender site set and the receiver site set.