Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual page 461

In one type of a hub-and-spoke design, only the hub site can reach every site in the
Example: Hub-and-Spoke
VPN. All other sites spokes can reach only the hub site. (More complex
VPN
hub-and-spoke designs are possible, but require additional configuration and route
targets to achieve.) In Figure 90 on page 426, Customer Site 1 is the hub site for VPN
A. As such it can reach both spokes, Customer Sites 2 and 3 through VRF A. Customer
Site 2 can reach only the hub, customer 1, through VRF C. Customer Site 3 can reach
only the hub, customer 1, through VRF E.
BGP sessions exist between PE 1 and PE 2 and between PE 1 and PE 3. In most
situations, BGP itself is fully meshed, but that level of complexity is not necessary
for this example. The MPLS paths through the service provider core are omitted for
clarity.
To configure route targets for this hub and spoke, you specify different import and
export route targets on the hub VRF. On the spoke VRFs, you switch these route
targets.
Route-target configuration on PE 1:
host3(config)#ip vrf vrfE
host3(config-vrf)#route-target both 777:1
host3(config-vrf)#exit
host3(config)#ip vrf vrfF
host3(config-vrf)#route-target both 777:2
host1(config)#virtual-router newyork
host1:newyork(config)#ip vrf vrfA
host1:newyork(config-vrf)#route-target export 777:25
host1:newyork(config-vrf)#route-target import 777:50
Chapter 5: Configuring BGP-MPLS Applications
Configuring BGP VPN Services
425