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Figure 87: Route Target Configuration for an Overlapping VPN
An interesting special case of an overlapping VPN is when two VRFs on the same
PE router belong to the same VPN as shown in Figure 88 on page 403. The
configuration of the VRF import and export route targets is the same as for the
example in Figure 87 on page 403.
If the export route target of one VRF (for example, the VPN AB VRF) matches the
import route target of another VRF (for example, the VPN A VRF), then BGP routes
are exported from one VRF to the other VRF; in this case from the VPN AB VRF to
the VPN A VRF. Consequently, traffic that arrives in one VRF is forwarded out another
VRF without going through the MPLS core network.
Figure 88: Overlapping VPNs on a Single PE
From a given CE router you can ping the local address of any VRF that has a VPN
overlapping another VPN to which the CE router belongs.
To achieve this internally, the router obtains the source address as follows:
Using Route Targets to Configure VPN Topologies
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Chapter 5: Configuring BGP-MPLS Applications