3com S7906E Instruccion De Instalación

 

1-14 

Figure 1-12 Scenario where the Level 2 carrier is an MPLS L3VPN service provider 

 

 

If there are equal cost routes between the Level 1 carrier and the Level 2 carrier, you are recommended 

to establish equal cost LSPs between them accordingly. 

 

In an MPLS L3VPN network, generally a service provider runs an MPLS L3VPN backbone and provides 

VPN services through PEs. VPN users are connected to PEs through CEs to access the MPLS L3VPN 

network. In this way, users in the same VPN at different sites can communicate with each other. In this 

scenario, user networks are ordinary IP networks and cannot be further divided into sub-VPNs.  

However, in actual applications, VPN user networks can be dramatically different in form and complexity, 

and a VPN user network may need to use VPNs to further group its users. The traditional solution to this 

request is to implement internal VPN configuration on the service provider’s PEs. This solution is easy 

to deploy, but it increases the network operation cost and brings issues on management and security 

because:  

z 

The number of VPNs that PEs must support will increase sharply.  

z 

Any modification of an internal VPN must be done through the service provider. 

The nested VPN technology offers a better solution. Its essence is to exchange VPNv4 routes between 

PEs and CEs of an ordinary MPLS L3VPN, and to allow VPN users to manage their own internal VPNs. 

 depicts a nested VPN network. On the service provider’s MPLS VPN network, there is a 

user VPN named VPN A. The user VPN contains two sub-VPNs, VPN A-1 and VPN A-2. The service 

provider PEs treat the user network as a common VPN user and will not join any sub-VPNs. The VPN 

user’s CE devices (CE 1, CE 2, CE 7 and CE 8) exchange VPNv4 routes that carry the sub-VPN routing 

information with the service provider PEs, implementing the propagation of the sub-VPN routing 

information throughout the user network.