OSPFv3: Differences between OSPFv2 and OSPFv3

OSPFv2 and OSPFv3 share many concepts however here are the major differences between the two protocols:

  • OSPFv3 is configured using interface commands, to enable an interface for a particular area and begin sending/receiving OSPF packets all you configure is ipv6 ospf 1 area 2 under the interface and that turns on the protocol and advertises the network on that port.   This also creates the ipv6 router ospf 1 in global configuration mode.
  • OSPFv3 can advertise multiple networks on an interface, if multiple secondary addresses are configured on the same interface all those networks are advertised as well.
  • OSPFv3 RID must be set, it will not dynamically learn or assign a RID if there are no IPv4 addresses, if there are some present it can still dynamically assign one based on the IPv4 address.
  • OSPFv3 has 3 flooding scopes:
    • Link local scope – new LSA type link LSA
    • Area scope – this is for LSAs flooded throughout a single OSPFv3 area.  Used by router, network, inter-area prefix, intra-area prefix, and inter-area router LSA type
    • AS scope – LSAs are flooded throughout the routing domain this is used for AS external LSAs
  • Multiple Instances per link – OSPFv3 supports multiple instances on a single interface where there are multiple routers connected to the same multi access segment, and you don’t want all routers to form neighborships but instead only specific routers, you can do this by instancing the OSPF configration under the interface.
  • Terminology – OSPFv3 uses the term link as represented in OSPFv2 as a network
  • Link local addresses are used on the interface to source all OSPF packets from with the exception of virtual links, virtual links used a globally scoped IPv6 address to source packets from
  • Authentication – OSPF does not support any method of authentication as AH and ESP are built into IPv6 natively
  • Networks in LSAs – OSPFv2 expresses prefixes as address/mask in its LSAs, OSPFv3 expresses prefixes as prefix/prefix length, where the default routes prefix length is 0.

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