OSPFv3 versus OSPFv2

OSPFv3 is different from regular OSPF in an number of ways:

  • Supports multiple address families: IPv4 is only supported in OSPFv2, OSPFv3 introduces support for IPv6 too!
  • Additional LSA Types: For carrying IPv6 addresses.
  • Removal of addressing semantics: Prefix information is no longer present in the OSPF packet headers. It is carried as a LSA payload instead, making the OSPF protocol address family independent.
  • LSA flooding: There is a new link-state type field that is used to determine the flooding scope of the LSA.
  • Packet format: OSPFv3 runs directly over IPv6; the number of fields in the packet header are reduced
  • Router ID: The Router ID is used to identify neighbours regardless of network type. The ID must always be assigned manually with OSPFv3 on Cisco routers.
  • Authentication: Neighbour authentication has removed and must be programed through IPSec extension headers.
  • Neighbour Adjacencies: OSPFv3 router communication is handled by IPv6 link local addressing. Neighbours are not automatically detected over non broadcast multi access interfaces and must be specified using a link local address. IPv6 allows for multiple subnets to be tied to a single interface, using link local addressing allows interfaces to form adjacency even if a common subnet is not shared.
  • Multiple Instance; OSPFv3 packets include a instance ID field that can be used to manipulate which routers are allowed to form adjacencies.



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