Operation Manual – MPLS L2VPN
H3C S9500 Series Routing Switches
Chapter 1 MPLS L2VPN Configuration
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III. Comparison with MPLS L3VPN
Compared with MPLS L3VPN, MPLS L2VPN has the following advantages:
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High scalability: MPLS L2VPN establishes only Layer 2 connections. It does not
involve the routing information of users. This greatly reduces the load of the PEs
and even the load of the whole service provider network, enabling carriers to
support more VPNs and to service more users.
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Guaranteed reliability and private routing information security: As no routing
information of users is involved, MPLS L2VPN neither tries to obtain nor
processes the routing information of users, guaranteeing the security of the user
VPN routing information.
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Support for multiple network layer protocols, such as IP, IPX, and SNA.
IV. Basic concepts of MPLS L2VPN
In MPLS L2VPN, the concepts and principles of CE, PE and P are the same as those in
MPLS L3VPN:
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Customer edge device (CE): A CE resides on a customer network and has one or
more interfaces directly connected with service provider networks. It can be a
router, a switch, or a host. It cannot "sense" the existence of any VPN, neither
does it need to support MPLS.
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Provider edge device (PE): A PE resides on a service provider network and
directly connects one or more CEs to the network. On an MPLS network, all VPN
processing occurs on the PEs.
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Provider (P) device: A P device is a backbone device on a service provider
network. It is not directly connected with any CE. It only needs to be equipped with
basic MPLS forwarding capabilities.
MPLS L2VPN uses label stacks to implement the transparent transmission of user
packets in the MPLS network.
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Outer label, also called tunnel label, is used to transfer packets from one PE to
another.
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Inner label, also called VC label, is used to identify different connections between
VPNs.
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Upon receiving packets, a PE determines to which CE the packets are to be
forwarded according to the VC labels.
Figure 1-2
illustrates how the label stack changes in the MPLS L2VPN forwarding
process.
