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DES-7200 Configuration Guide Chapter 2 Configuring BGP IP VPN
2-1
2 Configuring BGP IP VPN
2.1 Introduction to BGP/MPLS VPN
In traditional VPNs, private network data streams are generally transmitted over public networks
through GRE, L2TP, and PPTE tunnel protocols. As another implementation of VPN, BGP/MPLS
IP VPN can be considered as a VPN between Layer 2 and Layer 3. An LSP is a tunnel on the
public network that is set up through the MPLS LDP. In an MPLS VPN, the different branches of
private networks at different locations are connected together to form one network through LSPs.
The MPLS VPN also supports interworking between different VPNs. The implementation of VPN
through MPLS has natural edges. For VPN users, the work amount is largely reduced since no
special VPN devices are required to construct the VPN. Instead, the VPN users can directly use
traditional routers. For carriers, the MPLS VPN can be easily expanded.
As a highly effective technical platform for IP backbone networks, MPLS provides VPNs with
flexible and scalable technical foundations.
The L3VPN based on BGP/MPLS VPN has the following features:
1) The VPN tunnels are set up on the provider edge (PE) devices of network service providers
rather than the customer edge (CE) devices. The VPN routes are also transmitted between
PEs. In this manner, users are not required to maintain VPN information.
2) Directly utilize existing routing protocols. The setup of VPN tunnels and route advertising
are dynamically implemented, facilitating the expansion of VPNs.
3) Support address overlapping. Different VPN users can use the same address space.
4) On the network of service providers, VPN services are exchanged according to labels rather
than traditional routes.
5) Support the same security as user dedicated lines.
The BGP/MPLS VPN provides the following functions:
1) Adopt the LDP to set up LSPs on the backbone network. This process is generally
performed on the provider's network and completed when the topology becomes stable.
2) Forward data packets based on the pushed label and the local mapping table.