It is noteworthy to mention that on Cisco routers, if an OSPF process is run in a VRF then it automatically and unconditionally considers itself to be an ABR - it believes to be connected to a so-called MPLS Superbackbone (even though there may be no BGP/MPLS configured on the router at all).
This may pose problems if such a router is actually a part of a network that uses multiple areas. Consider the following scenario:
R1 (VRF) --- Link in Area 1 --- R2 --- Link in Area 0 --- R3
Here, R2 is obviously an ABR because it has two links, one in Area 0, the other in Area 1. R1 is, by all means, an internal router in Area 1. However, because R1 runs the link toward R2, and OSPF over this link, in a VRF, R1 considers itself to also be an ABR toward the MPLS Superbackbone.
As a result, R1 - thinking it is an ABR - will not place any networks from Area 0 nor from any other area behind R2 into its routing table, because by OSPF rules, an ABR processes only those inter-area routes (that is, LSA-3 and LSA-4) that have been received over an adjacency in Area 0, and R1 has no such adjacency. The end result will be that R1 will be unable to talk with any network outside its own Area 1.
This behavior on R1 is also deactivated by the
"capability vrf-lite" command.
Thus, "capability vrf-lite" has several effects:
- The router stops considering itself as the ABR connected to the MPLS Superbackbone
- The router will ignore the DN bit set in LSA-3, LSA-5 and LSA-7, and will not set this bit when doing redistribution into OSPF
- The router will ignore the tag value received in LSA-5 and LSA-7, and it will not set this value to any specific value when doing redistribution into OSPF.
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