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OSPF
Feature Overview
Figure 1 OSPF Connectivity Between VPN Client Sites and an MPLS VPN Backbone
Area 1 | Area 1 |
MPLS VPN | Area 2 | |
Superbackbone | ||
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Area 0
Area 0
Area 3
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When OSPF is used to connect PE and CE routers, all routing information learned from a VPN site is placed in the VPN routing and forwarding (VRF) instance associated with the incoming interface. The PE routers that attach to the VPN use the Border Gateway Protocol (BGP) to distribute VPN routes to each other. A CE router can then learn the routes to other sites in the VPN by peering with its attached PE router. The MPLS VPN superbackbone provides an additional level of routing hierarchy to interconnect the VPN sites running OSPF.
When OSPF routes are propagated over the MPLS VPN backbone, additional information about the prefix in the form of BGP extended communities (route type, domain ID extended communities) is appended to the BGP update. This community information is used by the receiving PE router to decide the type of
For basic information about how to configure an MPLS VPN, refer to:
http://www.cisco.com/univercd/cc/td/doc/product/software/ios120/120newft/120t/120t5/vpn.htm
Using a Sham-Link to Correct OSPF Backdoor Routing
Although OSPF
Cisco IOS Release 12.2(8)T
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