Open Shortest Path First for IPv6

Template:TOC-right A standard IP routing protocol, Open Shortest Path First, has been issued in a major new version, which can handle both Internet Protocol version 4 and Internet Protocol version 6. Familiarity with basic Open Shortest Path First (OSPF) and link state routing terminology is assumed in this article.

In some respects, readers will find that OSPF packets are simpler, in that this protocol allows IPv6 headers to do a number of things that previous OSPF did itself, occasionally duplicating IPv4 functionality. The packet headers do not contain source and destination addresses. Another simplification of the header is that OSPF-specific authentication has been removed, since the Authentication Header and Encapsulating Security Payload headers of IPv6 provide a quite adequate authentication function.

It remains true that most OSPF packets consist of a general-purpose header, and, in most packets, a variable number of Link State Advertisements. The most striking difference, however, is that the headers, and most of the LSAs, do not carry addresses, but a more compact identifier — which also gets around the problem of determining the type of address carried in an LSA. Actual addresses, IPv4 and IPv6, are only carried in Link State Updates.

There are many places, in all OSPF versions, where fields are 32 bits long. Simply because a field is 32 bits long, and may even be displayed in the format of an IPv4 address, does not mean that the field has to be a valid IPv4 address. Since OSPF for IPv6 continues to retain 32-bit identifiers in many places, even though all its actual addressing is IPv6, getting into the habit of thinking "identifier" rather than "address" will enormously simplify OSPF for IPv6 deployment.

Previous OSPF flooded information in what it called "networks", which were actually IPv4 subnets. OSPF for v6 floods on links, which may contain multiple subnets; note that from the IP standpoint, virtual local area networks (VLAN) are different links.

LSA formats

New LSAs have been created to carry IPv6
  addresses and prefixes.