Introduction To Ospf Multi-Instance - 3Com 8800 Configuration Manual

3Com Switch 8800 Configuration Guide
As shown in Figure 37-5, 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.
Upper VPN Upper VPN
Lower VPN Lower VPN
VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1
Figure 37-5 Hierarchical BGP/MPLS VPN

37.1.5 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.
Therefore IETF raised two new OSPF VPN extension drafts, to provide a complete
solution to SPPF problems in BGP/MPLS VPN application when OSPF is used as
PE-CE routing protocol. In this case, PE router must be able to run multiple OSPF
instances, each of which corresponds to one VPN instance, owns an individual
PE PE PE PE PE PE PE PE
UPE UPE UPE UPE UPE UPE UPE UPE
VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1
CE CE CE CE CE CE CE CE
CE CE CE CE CE CE CE CE
Chapter 37 BGP/MPLS VPN Configuration
MPLS backbone MPLS backbone
MPLS 骨干网 MPLS 骨干网 MPLS 骨干网 MPLS 骨干网 PE PE PE PE PE PE PE PE
network network
SPE SPE SPE SPE SPE SPE SPE SPE
UPE UPE UPE UPE UPE UPE UPE UPE
VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1 VPN1 Site1
CE CE CE CE CE CE CE CE
37-8
VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1 VPN2 Site1
CE CE CE CE CE CE CE CE