similarities to OSPFv2 include the following:

• Mechanisms for neighbor discovery and adjacency formation are identical.
• Operations of OSPFv3 over the RFC-compliant nonbroadcast multiaccess (NBMA) and point-to-multipoint topology modes are supported. OSPFv3 also supports the other modes from Cisco, such as point-to-point and broadcast, including the interface.
• LSA flooding and aging are the same for OSPFv2 and OSPFv3.
• OSPFv3 uses the same basic packet types as OSPFv2, such as hello packets, database description (also called database description packet), link-state request (LSR), link-state update (LSU), and LSA.

All of the optional capabilities of OSPF for IPv4, including on-demand circuit support, not-so-stubby areas (NSSAs), and the extensions to Multicast OSPF (MOSPF) are also supported in OSPF for IPv6.

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Content 8.4 IPv6 Routing 8.4.4 Differences Between OSPFv2 and OSPFv3 Differences between OSPFv2 and OSPFv3 include the following:

• OSPFv3 runs over a link
  • OSPF for IPv6 runs per link instead of the IPv4 behavior of per IP subnet. IPv6 uses the term “link” to indicate “a communication facility or medium over which nodes can communicate at the link layer.” Therefore, the terms “network” and “subnet” used in the IPv4 OSPF specification are replaced by “link.”
  • The network statement in the router subcommand mode of OSPFv2 is replaced by the ipv6 ospf process-id area area-id [instance instance-id] interface command.
• Link-local addresses are used
  • OSPFv3 uses IPv6 link-local addresses to identify the OSPFv3 adjacency neighbors. Therefore, when configuring the ipv6 ospf neighbor command, the IPv6 address used must be the link-local address of the neighbor.
• Multiple OSPFv3 instance support
  • Separate autonomous systems, each running OSPF, use a common link. A single link could belong to multiple areas.
  • OSPFv3 uses a new field, called the Instance ID, to allow multiple instances per link. To have two instances talk to each other, they must share the same instance ID. By default, the instance ID is set to 0.
• Multicast addresses
  • FF02::5—Represents all shortest path first (SPF) routers on the link-local scope, equivalent to 224.0.0.5 in OSPFv2.
  • FF02::6—Represents all designated routers (DRs) on the link-local scope, equivalent to 224.0.0.6 in OSPFv2.
• Removal of address semantics
  • IPv6 addresses are no longer present in the OSPF packet header (part of payload information).
  • Router LSAs and network LSAs do not carry IPv6 addresses.
  • The router ID, area ID, and link-state ID remain at 32 bits.
  • The DR and backup designated router (BDR) are identified by their router ID and not by their IP address.
• Security
  • OSPFv3 uses IPv6 Authentication Header (AH) and Encapsulating Security Payload (ESP) extension headers, instead of the variety of mechanisms defined in OSPFv2.
  • Authentication is no longer part of OSPF. It is now the job of IPv6 to make sure that the right level of authentication is in use.

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Content 8.4 IPv6 Routing 8.4.5 LSA Types for IPv6 OSPFv3 LSA features include the following:

• The LSA is composed of a router ID, area ID, and link-state ID. They are each 32 bits. Although they are written in dotted decimal, they are not derived from an IPv4 address.
• Router LSAs and network LSAs contain only 32-bit IDs. They do not contain addresses.
• LSAs have flooding scopes that define the diameter that they should be flooded to:
  • Link local: Flood all routers on the link.
  • Area: Flood all routers within an OSPF area.
  • Autonomous system: Flood all routers within the entire OSPF autonomous system.
• OSPFv3 supports the forwarding of unknown LSAs based on the flooding scope. This can be useful in an NSSA.
• OSPFv3 takes advantage of IPv6 multicasting, using FF02::5 for all OSPF routers, and FF02::6 for the OSPF DR and the OSPF BDR.

The two renamed LSAs are as follows:

• Interarea prefix LSAs for area border routers (ABRs) (type 3): Type 3 LSAs advertise internal networks to routers in other areas (interarea routes). Type 3 LSAs may represent a single network or a set of networks summarized into one advertisement. Only ABRs generate summary LSAs. In OSPF for IPv6, addresses for these LSAs are expressed as prefix, prefix length instead of address, mask. The default route is expressed as a prefix with length 0.
• Interarea router LSAs for autonomous system boundary routers (ASBRs) (type 4): Type 4 LSAs advertise the location of an ASBR. Routers that are trying to reach an external network use these advertisements to determine the best path to the next hop. ASBRs generate type 4 LSAs.

The two new LSAs in IPv6 are as follows:

• Link LSAs (type 8): Type 8 LSAs have link-local flooding scope and are never flooded beyond the link with which they are associated. Link LSAs provide the link-local address of the router to all other routers attached to the link. Link LSAs also inform other routers attached to the link of a list of IPv6 prefixes to associate with the link, and allow the router to assert a collection of options bits to associate with the network LSA that will be originated for the link.
• Intra-area prefix LSAs (type 9): A router can originate multiple intra-area prefix LSAs for each router or transit network, each with a unique link-state ID. The link-state ID for each intra-area prefix LSA describes its association to either the router LSA or the network LSA. The link-state ID also contains prefixes for stub and transit networks.

Web Links LSA Types for IPv6
http://cisco.com/en/US/products/sw/iosswrel/
ps5187/products_configuration_guide_chapter
09186a00801d660d.html#wp1132692

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Content 8.4 IPv6 Routing 8.4.6 Address Prefix and LSAs An address prefix occurs in almost all newly defined LSAs. The prefix is represented by three fields: Prefix Length, Prefix Options, and Address Prefix. In OSPF for IPv6, addresses for these LSAs are expressed as prefix, prefix length instead of address, mask. The default route is expressed as a prefix with length 0. Type 3 and type 9 LSAs carry all IPv6 prefix information, which, in IPv4, is included in router LSAs and network LSAs.

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Content 8.5 Implementing and Verifying OSPFv3 8.5.1 Configuring OSPFv3 in IPv6 Many OSPFv3 commands are similar to OSPFv2. In most cases, you simply either prefix or replace ip in the OSPF command with ipv6. For example, instead of using the ip address command to assign an IPv6 address, you use the ipv6 address command. To view the IPv6 routes, you issue the show ipv6 route command. The configuration of OSPFv3 is not a subcommand mode of the router ospf command as it is in OSPFv2 configuration. For example, instead of using the network area command to identify networks that are part of the OSPFv3 network, the interfaces are directly configured to specify that IPv6 networks are part of the OSPFv3 network. The following describes the steps to configure OSPF for IPv6: Step 1 Complete the OSPF network strategy and planning for your IPv6 network. For example, you must decide whether multiple areas are required. Step 2 Enable IPv6 unicast routing using the ipv6 unicast-routing command. Step 3 Enable IPv6 on the interface using the ipv6 ospf area command. Step 4 (Optional) Configure OPSFv3 interface specific settings, including area, router priority, and OSPFv3 path cost. Step 5 (Optional) Configure routing specifics from router configuration mode,