Information Technology Reference
In-Depth Information
The next sections describe the basic components of an MPLS VPN and the role of multi-
protocol BGP in distributing VPNv4 information. The following subjects are covered:
•
Components of an MPLS VPN
•
Virtual routing and forwarding instance
•
VPNv4 route and label propagation
•
Automatic route filtering
•
AS_PATH manipulation
Components of an MPLS VPN
Figure 10-5 shows the basic components of an MPLS VPN. Such a network has three types
of devices:
•
Customer edge (CE) router
•
Provider edge (PE) router
•
Provider (P) router
Note the similarity between Figure 10-5 and Figure 10-1. Typically a P device is a core
LSR, and a PE device is an LER.
Figure 10-5
Basic Components of an MPLS VPN
IP
IP
MPLS
CE
VPNa
CE
VPNa
P
R3
R1
R2
R5
R6
PE
PE
P
R4
CE
VPNb
R7
R8
CE
VPNb
Central to the architecture are the PE devices. These devices maintain rules of route redis-
tribution and the mappings of IPv4 prefixes in a VPN to VPNv4 prefixes in the core. In
Figure 10-5, PE devices R2 and R5 provide connectivity to both VPNs, VPNa and VPNb.
Configurations on these PE devices are made such that routes from VPNa are not redistrib-
uted to VPNb, and vice versa.
