OSPF Forward Address

OSPF Forward Address (FA):

  • works like BGP next-hop for OSPF external routes

  • advertised only if next-hop is on a not-passive and multiaccess interface

  • if there’s not a route to FA address, route is not installed

  • FA = 0.0.0.0 –> cost to ABR

  • FA <> 0.0.0.0 –> cost to FA address

  • NSSA –> FA is ASBR IP –> remove FA with “area 1 nssa no-summary translate type7 suppress-fa”

  • only router with highest RID advertises type 5+FA into area 0, remember it when manipulating FA or adding interfaces on ABR

Useful commands:

show ip ospf database external

show ip ospf border-routers

area 1 nssa no-summary translate type7 suppress-fa

###Links

The Effects of the Forwarding Address on Type 5 LSA Path Selection

OSPF Forwarding Address Suppression in Translated Type-5 LSAs

Common Routing Problem with OSPF Forwarding Address

 
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