Introduction To Ospf Multi-Instance - H3C S9500 Series Operation Manual

Routing switches

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Operation Manual – MPLS

H3C S9500 Series Routing Switches

primarily function to access the VPN clients at the edges. Congruous with the IP

network model, HoVPN model improves the scalability of BGP/MPLS VPN, and hence

allows lower-layer MPLS VPNs comprising low-end equipment to provide MPLS VPN

accessing and interconnect through the high-end MPLS VPN backbone.

As shown in Figure 3-5, the PEs directly connected with user devices are called UPE

(underlayer PE or user-end PE); the devices in the core network connected with the

UPEs are called SPE (superstratum PE or service-provider-end PE).

Hierarchical PEs have the same appearance as that of the traditional PEs and can

coexist with other PEs in the same MPLS network.

UPEs are responsible for user access; they only maintain the routes of directly

connected VPN sites, but not that of the remote sites. SPEs, however, are responsible

for the maintenance and advertisement of VPN routes; they maintain all the routes of

the VPNs connected by their UPEs, including the routes in both local and remote sites.

UPE and SPE are relative concepts. In a multi-layer PE architecture, an upper layer PE

is an SPE for its lower layer PE, and a lower layer PE is an UPE for its upper layer PE.

The MBGP runs between SPE and UPE can be either MP-IBGP or MP-EBGP,

depending on whether the SPE and the UPE are in the same AS.

Figure 3-5 Hierarchical BGP/MPLS VPN

3.1.5 Introduction to OSPF Multi-instance

As one of the most popular IGP routing protocols, OSPF is used as an internal routing

protocol in many VPNs. Using OSPF on PE-CE links brings convenience to you

because in this case CE routers only need to support OSPF protocol, without the need

of supporting other protocols, and network administrator only have to know the OSPF

protocol. If you want to transform conventional OSPF backbone into BGP/MPLS VPN,

using OSPF between PE and CE can simplify this transform process.

Chapter 3 BGP/MPLS VPN Configuration

MPLS backbone

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