A Route Distinguisher (RD) separates routes (one VRF for each customer routing table) of one customer from another. RD is prepended to each route (64-bit identifier is prepended) within a VRF to identify which VPN the route belongs to. An RD is carried along with a route via MP-BGP when exchanging VPN routes with other PE routers.
Route Target is a 64-bit identifier used as part of MP-BGP attribute (extended community) to identify which route should be exported or imported to specific VPN.Whereas route distinguishers are used to maintain uniqueness among identical routes in different VRFs, route targets can be used to share routes among them. We can apply route targets to a VRF to control the import and export of routes.
In case of configuring VRF lite, while RD is mandatory to be configured, RT configuration may not be required. Additionally, Route target may be categorized into 2 types – Export Route target and Import Route target respectively.
Below table details on differences between RD and RT –