OSPFv3
The acceptable account about OSPFv3 is that OSPFv2 was a complete acquisition agreement back development
began on OSPFv3. The bad account about OSPFv3 is that it is added circuitous in some means than
OSPFv2. But mostly the two protocols are artlessly altered because of the differences in the
underlying Layer 3 protocol. Fortunately, RFC 2740, which defines OSPFv3, goes into absolutely a bit
of detail in anecdotic these differences. (And this RFC is able-bodied account a apprehend to accretion a better
understanding of OSPFv3 than this affiliate can provide.)
Differences Amid OSPFv2 and OSPFv3
OSPFv2 and OSPFv3 allotment abounding key concepts, including best of their basal operations and the
concepts of acquaintance relationships, areas, interface types, basal links, metric calculations, and
many others. However, you should accept the cogent differences as well.
Key differences amid OSPFv2 and OSPFv3 accommodate these:
■ Configured application interface commands—Cisco IOS enables OSPFv3 application interface
subcommands, instead of application the OSPFv2 adjustment (using the arrangement command in router
configuration mode). To accredit OSPFv3 action ID (PID) 1 and breadth 2 on a accustomed interface,
the basal command is artlessly ipv6 ospf 1 breadth 2. Issuing this command additionally creates the ipv6
router ospf 1 command in all-around agreement mode.
■ Announcement assorted networks on an interface—If assorted IPv6 addresses are configured
on an interface, OSPFv3 advertises all of the agnate networks.
OSPFv3 769
■ OSPFv3 RID charge be set—OSPFv3 can automatically set its 32-bit RID based on the
configured IPv4 addresses, application the aforementioned rules for OSPFv2. However, if no IPv4 addresses
are configured, OSPFv3 cannot automatically accept its router ID. You charge manually
configure the RID afore OSPFv3 will start. By comparison, an OSPFv2 router ID is created
automatically if any IP interfaces are configured on a router.
■ Calamity scope—The ambit for calamity LSAs is one of three specific types in OSPFv3:
— Link-local scope—Used by the new LSA type, Articulation LSA.
— Breadth scope—For LSAs abounding throughout a distinct OSPFv3 area. Used by Router,
Network, Inter-Area Prefix, Inter-Area Router, and Intra-Area Prefix LSA types.
— AS scope—LSAs of this blazon are abounding throughout the acquisition domain; this is
used for AS External LSAs.
■ Assorted instances per link—OSPFv3 supports assorted instances on a link. For example,
suppose you accept four routers on an Ethernet segment: routers A, B, 1, and 2. You want
routers A and B to anatomy adjacencies (become neighbors), and routers 1 and 2 to become
neighbors, but you do not appetite routers A and B to anatomy neighborships with routers 1 and 2.
OSPFv3 supports this blazon of adjacency scoping. The ambit of instance numbers is 0–255,
and the command architecture on the interface is, for example, ipv6 ospf 1 breadth 0 instance 33. The
instance charge bout on all routers that are to become adjoining on a link.
■ Terminology—OSPFv3 uses the appellation articulation for what OSPFv2 calls a network.
■ Sources packets from link-local addresses—With the barring of basal links, OSPFv3 uses
link-local addresses for all communications amid neighbors and sources packets from linklocal
addresses. On basal links, OSPFv3 sources packets from a globally scoped IPv6 address.
■ Authentication—OSPFv2 natively supports three affidavit types: null, simple
password, and MD5. OSPFv3, however, does not itself accommodate authentication, because IPv6
covers this claim with its centralized abutment for AH and ESP protocols, as declared in
more detail after in this chapter.
■ Networks in LSAs—Whereas OSPFv2 expresses networks in LSAs as [address, mask],
OSPFv3 expresses networks in LSAs as [prefix, prefix length]. The absence router is expressed
with a prefix breadth of 0.
Virtual Links, Abode Summarization, and Other OSPFv3 Features
Many OSPFv3 appearance are conceptually identical to OSPFv2 and alter alone hardly in their
configuration. Some of these appearance accommodate the following:
■ Basal links (which point to router IDs)
■ Abode summarization by area
■ Abode summarization in the acquisition process
■ Stub breadth configuration
■ NSSA configuration
■ Advertising, or not advertising, a arbitrary application the breadth ambit [advertise | not-advertise]
command
■ OSPF arrangement types and interface configuration
■ Router antecedence agreement for multiaccess networks, to access DR and BDR elections
■ Best OSPF appearance commands