3com 3031 Instruccion De Instalación
696
C
HAPTER
54: BGP/MPLS VPN C
ONFIGURATION
There are high performance requirements in routing and forwarding on the PEs at
the higher level of MPLS VPN, because they are primarily used for connecting the
backbone networks and providing access service for huge VPN clients. However,
such requirements are relatively low for PEs at the lower level of the network as
they primarily function to access the VPN clients at the edges. In agreement 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 access and interconnect via the high-end MPLS VPN backbone.
the higher level of MPLS VPN, because they are primarily used for connecting the
backbone networks and providing access service for huge VPN clients. However,
such requirements are relatively low for PEs at the lower level of the network as
they primarily function to access the VPN clients at the edges. In agreement 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 access and interconnect via the high-end MPLS VPN backbone.
Figure 169 Hierarchical BGP/MPLS VPN
Introduction to
Multi-Role Host Features
As the VPN attribute of a packet that enters PE from CE is determined by the VPN
bound with the incoming interface, it in essence determines that all the CEs that
obtain the forwarding service of PE via the same incoming interface must belong
to the same VPN. In the actual networking environments, however, there is the
need for a CE to access multiple VPNs via the same physical interface. Such a
requirement can be accomplished by setting different logical interfaces, but such a
stopgap solution will increase the number of configurations and are limited in
application. In the process of solving this problem, the concept of multi-role host
was introduced. It distinguishes the VPNs that the packets will access by
configuring the policy route on the basis of IP address. As for the PE-CE
downstream traffic, this function is implemented via static routing. The static
routing in a multi-role host application is different from the regular static routes in
the sense that it enables a logical interface to access multiple VPNs by making use
of the static route on a VPN to specify an interface in some other VPN as the
outgoing interface.
bound with the incoming interface, it in essence determines that all the CEs that
obtain the forwarding service of PE via the same incoming interface must belong
to the same VPN. In the actual networking environments, however, there is the
need for a CE to access multiple VPNs via the same physical interface. Such a
requirement can be accomplished by setting different logical interfaces, but such a
stopgap solution will increase the number of configurations and are limited in
application. In the process of solving this problem, the concept of multi-role host
was introduced. It distinguishes the VPNs that the packets will access by
configuring the policy route on the basis of IP address. As for the PE-CE
downstream traffic, this function is implemented via static routing. The static
routing in a multi-role host application is different from the regular static routes in
the sense that it enables a logical interface to access multiple VPNs by making use
of the static route on a VPN to specify an interface in some other VPN as the
outgoing interface.
Introduction to OSPF
multi-instance
As one of the most popular IGP routing protocols, OSPF is used as internal routing
protocol in many VPNs. If OSPF is also used on PE-CE links, then CE routers only
need to support OSPF protocol. If you want to transform conventional OSPF
backbone into BGP/MPLS VPN, the OSPF can simplify this process.
protocol in many VPNs. If OSPF is also used on PE-CE links, then CE routers only
need to support OSPF protocol. If you want to transform conventional OSPF
backbone into BGP/MPLS VPN, the OSPF can simplify this process.
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, one OSPF instance corresponds to one VPN instance. It owns
SPPF problems in BGP/MPLS VPN application when OSPF is used as PE-CE routing
protocol. In this case, one OSPF instance corresponds to one VPN instance. It owns
MPLS backbone
PE
PE
SPE
Router
Upper VPN
Lower VPN
UPE
CE
CE
CE
CE
VPN1 Site1
VPN2 Site1
VPN1 Site1
VPN2 Site1
UPE
Lower VPN
MPLS backbone
PE
PE
SPE
Router
Upper VPN
Lower VPN
UPE
CE
CE
CE
CE
VPN1 Site1
VPN2 Site1
VPN1 Site1
VPN2 Site1
UPE
Lower VPN