H3C Technologies H3C S10500 Series Switches - Manual (Page 249)

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1. SPE-UPE
The MP-BGP running between SPE and UPE can be either MP-iBGP or MP-eBGP. Which one to use
depends on whether the UPE and SPE belong to a same AS.
With MP-iBGP, to advertise routes between iBGP peers, the SPE acts as the RR and advertises routes from
iBGP peer UPE to iBGP peer SPE. However, it does not act as the RR of the other PEs.
2. Recursion and extension of HoVPN
HoVPN supports HoPE recursion:
• A HoPE can act as a UPE to form a new HoPE with an SPE.
• A HoPE can act as an SPE to form a new HoPE with multiple UPEs.
• HoVPN supports multi-level recursion.
With recursion of HoPEs, a VPN can, in theory, be extended infinitely.
Figure 67 Recursion of HoPEs
Figure 67 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.
NOTE:
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 the 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, while each UPE maintains only VPN routes
of its directly connected sites. The number of routes maintained by the MPE is between the two.
OSPF VPN extension
NOTE:
This section focuses on the OSPF VPN extension. For more information about OSPF, see Layer 3—IP
Routing Configuration Guide.