Ospf Vpn Extension - HP 10500 SERIES Configuration Manual

Figure 27 Recursion of HoPEs
Figure 27 shows a three-level HoPE. The PE in the middle is called the middle-level PE (MPE). MP-BGP
runs between SPE and MPE, and between MPE and UPE.
The term "MPE" does not really exist in a HoVPN model. It is used here just for the convenience of
description.
MP-BGP advertises all VPN routes of the UPEs to the SPEs, and advertises the default routes of the VPN
instance of the SPEs or the VPN routes permitted by the routing policies to the UPEs.
The SPE maintains the VPN routes of all sites in the HoVPN. Each UPE maintains only VPN routes of its
directly connected sites. An MPE has fewer routes than the SPE but has more routes than a UPE.

OSPF VPN extension

This section focuses on the OSPF VPN extension. For more information about OSPF, see Layer 3—IP
Routing Configuration Guide.
OSPF for VPNs on a PE
OSPF is a prevalent IGP protocol. It often runs between PE and CE to simplify CE configuration and
management because the CEs only need to support OSPF. In addition, if the customers require MPLS
L3VPN services through conventional OSPF backbone, using OSPF between PE and CE can simplify the
transition.
For OSPF to run between CE and PE, the PE must support multiple OSPF processes. Each OSPF process
must correspond to a VPN instance and have its own interface and routing table.
Details of OSPF configuration between PE and CE are describe here:
Configuration of OSPF areas between PE and CE
•
The OSPF area between a PE and a CE can be either a non-backbone area or a backbone area.
In the OSPF VPN extension application, the MPLS VPN backbone is considered the backbone area
(area 0). The area 0 of each VPN site must be connected to the MPLS VPN backbone because
OSPF requires that the backbone area be contiguous.
If a VPN site contains an OSPF area 0, the connected PE must be connected to the backbone area
of the VPN site through area 0. You can configure a logical connection by using a virtual link.
• BGP/OSPF interaction
PEs advertise VPN routes to each other through BGP and to CEs through OSPF.
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