3com S7906E 설치 설명서

 

1-2 

Figure 1-1 A BGP/MPLS VPN implementation 

 

 

CEs and PEs mark the boundary between the service providers and the customers. 

A CE is usually a router. After a CE establishes adjacency with a directly connected PE, it redistributes 

its VPN routes to the PE and learns remote VPN routes from the PE. A CE and a PE use BGP/IGP to 

exchange routing information. You can also configure static routes between them. 

After a PE learns the VPN routing information of a CE, it uses BGP to exchange VPN routing 

information with other PEs. A PE maintains routing information about only VPNs that are directly 

connected, rather than all VPN routing information on the provider network. 

A P router maintains only routes to PEs. It does not need to know anything about VPN routing 

information. 

When VPN traffic travels over the MPLS backbone, the ingress PE functions as the ingress LSR, the 

egress PE functions as the egress LSR, while P routers function as the transit LSRs. 

You can use S7900E series switches as the CEs in a BGP/MPLS VPN implementation.  

Site is often mentioned in the VPN, whose meanings are described as follows: 

z 

A site is a group of IP systems with IP connectivity that does not rely on any service provider 

network to implement. 

z 

The classification of a site depends on the topology relationship of the devices, rather than the 

geographical positions, though the devices at a site are adjacent to each other geographically in 

most cases.  

z 

The devices at a site can belong to multiple VPNs, namely, a site can belong to multiple VPNs. 

z 

A site is connected to a provider network through one or more CEs. A site can contain many CEs, 

but a CE can belong to only one site.  

Sites connected to the same provider network can be classified into different sets by policies. Only the 

sites in the same set can access each other through the provider network. Such a set is called a VPN.