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RFC 5340

 
 
 

OSPF for IPv6

Part 4 of 4, p. 68 to 94
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A.4.  LSA Formats

   This document defines eight distinct types of LSAs.  Each LSA begins
   with a standard 20-byte LSA header.  This header is explained in
   Appendix A.4.2.  Succeeding sections describe each LSA type
   individually.

   Each LSA describes a piece of the OSPF routing domain.  Every router
   originates a router-LSA.  A network-LSA is advertised for each link
   by its Designated Router.  A router's link-local addresses are
   advertised to its neighbors in link-LSAs.  IPv6 prefixes are
   advertised in intra-area-prefix-LSAs, inter-area-prefix-LSAs, AS-
   external-LSAs, and NSSA-LSAs.  Location of specific routers can be
   advertised across area boundaries in inter-area-router-LSAs.  All
   LSAs are then flooded throughout the OSPF routing domain.  The

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   flooding algorithm is reliable, ensuring that all routers common to a
   flooding scope have the same collection of LSAs associated with that
   flooding scope.  (See Section 4.5 for more information concerning the
   flooding algorithm.)  This collection of LSAs is called the link-
   state database.

   From the link-state database, each router constructs a shortest-path
   tree with itself as root.  This yields a routing table (see Section
   11 of [OSPFV2]).  For details on the routing table build process, see
   Section 4.8.

A.4.1.  IPv6 Prefix Representation

   IPv6 addresses are bit strings of length 128.  IPv6 routing
   protocols, and OSPF for IPv6 in particular, advertise IPv6 address
   prefixes.  IPv6 address prefixes are bit strings whose length ranges
   between 0 and 128 bits (inclusive).

   Within OSPF, IPv6 address prefixes are always represented by a
   combination of three fields: PrefixLength, PrefixOptions, and Address
   Prefix.  PrefixLength is the length in bits of the prefix.
   PrefixOptions is an 8-bit field describing various capabilities
   associated with the prefix (see Appendix A.4.1.1).  Address Prefix is
   an encoding of the prefix itself as an even multiple of 32-bit words,
   padding with zero bits as necessary.  This encoding consumes
   ((PrefixLength + 31) / 32) 32-bit words.

   The default route is represented by a prefix of length 0.

   Examples of IPv6 Prefix representation in OSPF can be found in
   Appendix A.4.5, Appendix A.4.7, Appendix A.4.8, Appendix A.4.9, and
   Appendix A.4.10.

A.4.1.1.  Prefix Options

   Each prefix is advertised along with an 8-bit field of capabilities.
   These serve as input to the various routing calculations.  For
   example, they can indicate that prefixes are to be ignored in some
   cases or are to be marked as not readvertisable in others.

                     0  1  2  3  4  5  6  7
                    +--+--+--+--+--+-+--+--+
                    |  |  |  |DN| P|x|LA|NU|
                    +--+--+--+--+--+-+--+--+

                          The PrefixOptions Field

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   NU-bit
      The "no unicast" capability bit.  If set, the prefix should be
      excluded from IPv6 unicast calculations.  If not set, it should be
      included.

   LA-bit
      The "local address" capability bit.  If set, the prefix is
      actually an IPv6 interface address of the Advertising Router.
      Advertisement of local interface addresses is described in
      Section 4.4.3.9.  An implementation MAY also set the LA-bit for
      prefixes advertised with a host PrefixLength (128).

   x-bit
      This bit was previously defined as a "multicast" capability bit.
      However, the use was never adequately specified and has been
      deprecated for OSPFv3.  The bit should be set to 0 and ignored
      when received.  It may be reassigned in the future.

   P-bit
      The "propagate" bit.  Set on NSSA area prefixes that should be
      readvertised by the translating NSSA area border [NSSA].

   DN-bit
      This bit controls an inter-area-prefix-LSAs or AS-external-LSAs
      re-advertisement in a VPN environment as specified in [DN-BIT].

A.4.2.  The LSA Header

   All LSAs begin with a common 20-byte header.  This header contains
   enough information to uniquely identify the LSA (LS type, Link State
   ID, and Advertising Router).  Multiple instances of the LSA may exist
   in the routing domain at the same time.  It is then necessary to
   determine which instance is more recent.  This is accomplished by
   examining the LS age, LS sequence number, and LS checksum fields that
   are also contained in the LSA header.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |           LS Type             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                              The LSA Header

   LS Age
      The time in seconds since the LSA was originated.

   LS Type
      The LS type field indicates the function performed by the LSA.
      The high-order three bits of LS type encode generic properties of
      the LSA, while the remainder (called LSA function code) indicate
      the LSA's specific functionality.  See Appendix A.4.2.1 for a
      detailed description of LS type.

   Link State ID
      The originating router's identifier for the LSA.  The combination
      of the Link State ID, LS type, and Advertising Router uniquely
      identify the LSA in the link-state database.

   Advertising Router
      The Router ID of the router that originated the LSA.  For example,
      in network-LSAs this field is equal to the Router ID of the
      network's Designated Router.

   LS sequence number
      Successive instances of an LSA are given successive LS sequence
      numbers.  The sequence number can be used to detect old or
      duplicate LSA instances.  See Section 12.1.6 in [OSPFV2] for more
      details.

   LS checksum
      The Fletcher checksum of the complete contents of the LSA,
      including the LSA header but excluding the LS age field.  See
      Section 12.1.7 in [OSPFV2] for more details.

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   length
      The length in bytes of the LSA.  This includes the 20-byte LSA
      header.

A.4.2.1.  LSA Type

   The LS type field indicates the function performed by the LSA.  The
   high-order three bits of LS type encode generic properties of the
   LSA, while the remainder (called LSA function code) indicate the
   LSA's specific functionality.  The format of the LS type is as
   follows:

              0  1  2  3  4  5  6  7  8  9  0  1  2  3  4  5
            +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
            |U |S2|S1|           LSA Function Code          |
            +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+

                                 LSA Type

   The U-bit indicates how the LSA should be handled by a router that
   does not recognize the LSA's function code.  Its values are:

        U-bit   LSA Handling
        -------------------------------------------------------------
        0       Treat the LSA as if it had link-local flooding scope
        1       Store and flood the LSA as if the type is understood

                                   U-Bit

   The S1 and S2 bits indicate the flooding scope of the LSA.  The
   values are:

     S2  S1   Flooding Scope
     -------------------------------------------------------------
     0  0    Link-Local Scoping - Flooded only on originating link
     0  1    Area Scoping - Flooded only in originating area
     1  0    AS Scoping - Flooded throughout AS
     1  1    Reserved

                              Flooding Scope

   The LSA function codes are defined as follows.  The origination and
   processing of these LSA function codes are defined elsewhere in this
   document, except for the NSSA-LSA (see [NSSA]) and 0x2006, which was
   previously used by MOSPF (see [MOSPF]).  MOSPF has been deprecated
   for OSPFv3.  As shown below, each LSA function b code also implies a
   specific setting for the U, S1, and S2 bits.

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            LSA Function Code   LS Type   Description
            ----------------------------------------------------
            1                   0x2001    Router-LSA
            2                   0x2002    Network-LSA
            3                   0x2003    Inter-Area-Prefix-LSA
            4                   0x2004    Inter-Area-Router-LSA
            5                   0x4005    AS-External-LSA
            6                   0x2006    Deprecated (may be reassigned)
            7                   0x2007    NSSA-LSA
            8                   0x0008    Link-LSA
            9                   0x2009    Intra-Area-Prefix-LSA

                             LSA Function Code

A.4.3.  Router-LSAs

   Router-LSAs have LS type equal to 0x2001.  Each router in an area
   originates one or more router-LSAs.  The complete collection of
   router-LSAs originated by the router describe the state and cost of
   the router's interfaces to the area.  For details concerning the
   construction of router-LSAs, see Section 4.4.3.2.  Router-LSAs are
   only flooded throughout a single area.

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       0                    1                   2                   3
       0 1 2 3  4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age               |0|0|1|         1               |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                            |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                          |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                          |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum             |            Length             |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  0  |Nt|x|V|E|B|            Options                            |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type       |       0       |          Metric               |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Interface ID                              |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Neighbor Interface ID                        |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Neighbor Router ID                          |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             ...                                |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type       |       0       |          Metric               |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                      Interface ID                              |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                   Neighbor Interface ID                        |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Neighbor Router ID                          |
      +-+-+-+--+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             ...                                |

                             Router-LSA Format

   A single router may originate one or more router-LSAs, distinguished
   by their Link State IDs (which are chosen arbitrarily by the
   originating router).  The Options field and V, E, and B bits should
   be the same in all router-LSAs from a single originator.  However, in
   the case of a mismatch, the values in the LSA with the lowest Link
   State ID take precedence.  When more than one router-LSA is received
   from a single router, the links are processed as if concatenated into
   a single LSA.

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   Bit V
      When set, the router is an endpoint of one or more fully adjacent
      virtual links having the described area as transit area (V is for
      virtual link endpoint).

   Bit E
      When set, the router is an AS boundary router (E is for external).

   Bit B
      When set, the router is an area border router (B is for border).

   Bit x
      This bit was previously used by MOSPF (see [MOSPF]) and has been
      deprecated for OSPFv3.  The bit should be set to 0 and ignored
      when received.  It may be reassigned in the future.

   Bit Nt
      When set, the router is an NSSA border router that is
      unconditionally translating NSSA-LSAs into AS-external-LSAs (Nt
      stands for NSSA translation).  Note that such routers have their
      NSSATranslatorRole area configuration parameter set to Always.
      (See [NSSA].)

   Options
      The optional capabilities supported by the router, as documented
      in Appendix A.2.

   The following fields are used to describe each router interface.  The
   Type field indicates the kind of interface being described.  It may
   be an interface to a transit network, a point-to-point connection to
   another router, or a virtual link.  The values of all the other
   fields describing a router interface depend on the interface's Type
   field.

   Type
      The kind of interface being described.  One of the following:

             Type   Description
             ---------------------------------------------------
             1      Point-to-point connection to another router
             2      Connection to a transit network
             3      Reserved
             4      Virtual link

                              Router Link Types

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   Metric
      The cost of using this router interface for outbound traffic.

   Interface ID
      The Interface ID assigned to the interface being described.  See
      Section 4.1.2 and Appendix C.3.

   Neighbor Interface ID
      The Interface ID the neighbor router has associated with the link,
      as advertised in the neighbor's Hello packets.  For transit (type
      2) links, the link's Designated Router is the neighbor described.
      For other link types, the sole adjacent neighbor is described.

   Neighbor Router ID
      The Router ID the of the neighbor router.  For transit (type 2)
      links, the link's Designated Router is the neighbor described.
      For other link types, the sole adjacent neighbor is described.

   For transit (Type 2) links, the combination of Neighbor Interface ID
   and Neighbor Router ID allows the network-LSA for the attached link
   to be found in the link-state database.

A.4.4.  Network-LSAs

   Network-LSAs have LS type equal to 0x2002.  A network-LSA is
   originated for each broadcast and NBMA link in the area that includes
   two or more adjacent routers.  The network-LSA is originated by the
   link's Designated Router.  The LSA describes all routers attached to
   the link including the Designated Router itself.  The LSA's Link
   State ID field is set to the Interface ID that the Designated Router
   has been advertising in Hello packets on the link.

   The distance from the network to all attached routers is zero.  This
   is why the Metric fields need not be specified in the network-LSA.
   For details concerning the construction of network-LSAs, see
   Section 4.4.3.3.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |0|0|1|          2              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |              Options                          |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Attached Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             ...                               |

                            Network-LSA Format

   Attached Router
      The Router IDs of each of the routers attached to the link.
      Actually, only those routers that are fully adjacent to the
      Designated Router are listed.  The Designated Router includes
      itself in this list.  The number of routers included can be
      deduced from the LSA header's length field.

A.4.5.  Inter-Area-Prefix-LSAs

   Inter-area-prefix-LSAs have LS type equal to 0x2003.  These LSAs are
   the IPv6 equivalent of OSPF for IPv4's type 3 summary-LSAs (see
   Section 12.4.3 of [OSPFV2]).  Originated by area border routers, they
   describe routes to IPv6 address prefixes that belong to other areas.
   A separate inter-area-prefix-LSA is originated for each IPv6 address
   prefix.  For details concerning the construction of inter-area-
   prefix-LSAs, see Section 4.4.3.4.

   For stub areas, inter-area-prefix-LSAs can also be used to describe a
   (per-area) default route.  Default summary routes are used in stub
   areas instead of flooding a complete set of external routes.  When
   describing a default summary route, the inter-area-prefix-LSA's
   PrefixLength is set to 0.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |0|0|1|          3              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                  Metric                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | PrefixLength  | PrefixOptions |              0                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Inter-Area-Prefix-LSA Format

   Metric
      The cost of this route.  Expressed in the same units as the
      interface costs in router-LSAs.  When the inter-area-prefix-LSA is
      describing a route to a range of addresses (see Appendix C.2), the
      cost is set to the maximum cost to any reachable component of the
      address range.

   PrefixLength, PrefixOptions, and Address Prefix
      Representation of the IPv6 address prefix, as described in
      Appendix A.4.1.

A.4.6.  Inter-Area-Router-LSAs

   Inter-area-router-LSAs have LS type equal to 0x2004.  These LSAs are
   the IPv6 equivalent of OSPF for IPv4's type 4 summary-LSAs (see
   Section 12.4.3 of [OSPFV2]).  Originated by area border routers, they
   describe routes to AS boundary routers in other areas.  To see why it
   is necessary to advertise the location of each ASBR, consult Section
   16.4 in [OSPFV2].  Each LSA describes a route to a single router.
   For details concerning the construction of inter-area-router-LSAs,
   see Section 4.4.3.5.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |0|0|1|        4                |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                 Options                       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |      0        |                 Metric                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Destination Router ID                      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Inter-Area-Router-LSA Format

   Options
      The optional capabilities supported by the router, as documented
      in Appendix A.2.

   Metric
      The cost of this route.  Expressed in the same units as the
      interface costs in router-LSAs.

   Destination Router ID
      The Router ID of the router being described by the LSA.

A.4.7.  AS-External-LSAs

   AS-external-LSAs have LS type equal to 0x4005.  These LSAs are
   originated by AS boundary routers and describe destinations external
   to the AS.  Each LSA describes a route to a single IPv6 address
   prefix.  For details concerning the construction of AS-external-LSAs,
   see Section 4.4.3.6.

   AS-external-LSAs can be used to describe a default route.  Default
   routes are used when no specific route exists to the destination.
   When describing a default route, the AS-external-LSA's PrefixLength
   is set to 0.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |0|1|0|          5              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         |E|F|T|                Metric                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | PrefixLength  | PrefixOptions |     Referenced LS Type        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +-                                                             -+
      |                                                               |
      +-                Forwarding Address (Optional)                -+
      |                                                               |
      +-                                                             -+
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |              External Route Tag (Optional)                    |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               Referenced Link State ID (Optional)             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          AS-external-LSA Format

   bit E
      The type of external metric.  If bit E is set, the metric
      specified is a Type 2 external metric.  This means the metric is
      considered larger than any intra-AS path.  If bit E is zero, the
      specified metric is a Type 1 external metric.  This means that it
      is expressed in the same units as other LSAs (i.e., the same units
      as the interface costs in router-LSAs).

   bit F
      If set, a Forwarding Address has been included in the LSA.

   bit T
      If set, an External Route Tag has been included in the LSA.

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   Metric
      The cost of this route.  Interpretation depends on the external
      type indication (bit E above).

   PrefixLength, PrefixOptions, and Address Prefix
      Representation of the IPv6 address prefix, as described in
      Appendix A.4.1.

   Referenced LS Type
      If non-zero, an LSA with this LS type is to be associated with
      this LSA (see Referenced Link State ID below).

   Forwarding address
      A fully qualified IPv6 address (128 bits).  Included in the LSA if
      and only if bit F has been set.  If included, data traffic for the
      advertised destination will be forwarded to this address.  It MUST
      NOT be set to the IPv6 Unspecified Address (0:0:0:0:0:0:0:0) or an
      IPv6 Link-Local Address (Prefix FE80/10).  While OSPFv3 routes are
      normally installed with link-local addresses, an OSPFv3
      implementation advertising a forwarding address MUST advertise a
      global IPv6 address.  This global IPv6 address may be the next-hop
      gateway for an external prefix or may be obtained through some
      other method (e.g., configuration).

   External Route Tag
      A 32-bit field that MAY be used to communicate additional
      information between AS boundary routers.  Included in the LSA if
      and only if bit T has been set.

   Referenced Link State ID
      Included if and only if Reference LS Type is non-zero.  If
      included, additional information concerning the advertised
      external route can be found in the LSA having LS type equal to
      "Referenced LS Type", Link State ID equal to "Referenced Link
      State ID", and Advertising Router the same as that specified in
      the AS-external-LSA's link-state header.  This additional
      information is not used by the OSPF protocol itself.  It may be
      used to communicate information between AS boundary routers.  The
      precise nature of such information is outside the scope of this
      specification.

   All, none, or some of the fields labeled Forwarding address, External
   Route Tag, and Referenced Link State ID MAY be present in the AS-
   external-LSA (as indicated by the setting of bit F, bit T, and
   Referenced LS Type respectively).  When present, Forwarding Address
   always comes first, External Route Tag next, and the Referenced Link
   State ID last.

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A.4.8.  NSSA-LSAs

   NSSA-LSAs have LS type equal to 0x2007.  These LSAs are originated by
   AS boundary routers within an NSSA and describe destinations external
   to the AS that may or may not be propagated outside the NSSA (refer
   to [NSSA]).  Other than the LS type, their format is exactly the same
   as AS-external LSAs as described in Appendix A.4.7.

   A global IPv6 address MUST be selected as forwarding address for
   NSSA-LSAs that are to be propagated by NSSA area border routers.  The
   selection should proceed the same as OSPFv2 NSSA support [NSSA] with
   additional checking to ensure IPv6 link-local address are not
   selected.

A.4.9.  Link-LSAs

   Link-LSAs have LS type equal to 0x0008.  A router originates a
   separate link-LSA for each attached physical link.  These LSAs have
   link-local flooding scope; they are never flooded beyond the
   associated link.  Link-LSAs have three purposes:

   1.  They provide the router's link-local address to all other routers
       attached to the link.

   2.  They inform other routers attached to the link of a list of IPv6
       prefixes to associate with the link.

   3.  They allow the router to advertise a collection of Options bits
       in the network-LSA originated by the Designated Router on a
       broadcast or NBMA link.

   For details concerning the construction of links-LSAs, see
   Section 4.4.3.8.

   A link-LSA's Link State ID is set equal to the originating router's
   Interface ID on the link.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |0|0|0|          8              |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     Advertising Router                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                     LS Sequence Number                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |            Length             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Rtr Priority  |                Options                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +-                                                             -+
      |                                                               |
      +-                Link-local Interface Address                 -+
      |                                                               |
      +-                                                             -+
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                         # prefixes                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  PrefixLength | PrefixOptions |             0                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  PrefixLength | PrefixOptions |             0                 |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                        Address Prefix                         |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                              Link-LSA Format

   Rtr Priority
      The Router Priority of the interface attaching the originating
      router to the link.

   Options
      The set of Options bits that the router would like set in the
      network-LSA that will be originated by the Designated Router on
      broadcast or NBMA links.

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   Link-local Interface Address
      The originating router's link-local interface address on the link.

   # prefixes
      The number of IPv6 address prefixes contained in the LSA.

   The rest of the link-LSA contains a list of IPv6 prefixes to be
   associated with the link.

   PrefixLength, PrefixOptions, and Address Prefix
      Representation of an IPv6 address prefix, as described in
      Appendix A.4.1.

A.4.10.  Intra-Area-Prefix-LSAs

   Intra-area-prefix-LSAs have LS type equal to 0x2009.  A router uses
   intra-area-prefix-LSAs to advertise one or more IPv6 address prefixes
   that are associated with a local router address, an attached stub
   network segment, or an attached transit network segment.  In IPv4,
   the first two were accomplished via the router's router-LSA and the
   last via a network-LSA.  In OSPF for IPv6, all addressing information
   that was advertised in router-LSAs and network-LSAs has been removed
   and is now advertised in intra-area-prefix-LSAs.  For details
   concerning the construction of intra-area-prefix-LSA, see
   Section 4.4.3.9.

   A router can originate multiple intra-area-prefix-LSAs for each
   router or transit network.  Each such LSA is distinguished by its
   unique Link State ID.

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       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           LS Age              |0|0|1|            9            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Link State ID                           |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    Advertising Router                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    LS Sequence Number                         |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |        LS Checksum            |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |         # Prefixes            |     Referenced LS Type        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Referenced Link State ID                     |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |               Referenced Advertising Router                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  PrefixLength | PrefixOptions |          Metric               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Address Prefix                          |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |  PrefixLength | PrefixOptions |          Metric               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                       Address Prefix                          |
      |                             ...                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                       Intra-Area-Prefix LSA Format

   # prefixes
      The number of IPv6 address prefixes contained in the LSA.

   Referenced LS Type, Referenced Link State ID, and Referenced
      Advertising Router
      Identifies the router-LSA or network-LSA with which the IPv6
      address prefixes should be associated.  If Referenced LS Type is
      0x2001, the prefixes are associated with a router-LSA, Referenced
      Link State ID should be 0, and Referenced Advertising Router
      should be the originating router's Router ID.  If Referenced LS
      Type is 0x2002, the prefixes are associated with a network-LSA,
      Referenced Link State ID should be the Interface ID of the link's
      Designated Router, and Referenced Advertising Router should be the
      Designated Router's Router ID.

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   The rest of the intra-area-prefix-LSA contains a list of IPv6
   prefixes to be associated with the router or transit link, as well as
   their associated costs.

   PrefixLength, PrefixOptions, and Address Prefix
      Representation of an IPv6 address prefix, as described in
      Appendix A.4.1.

   Metric
      The cost of this prefix.  Expressed in the same units as the
      interface costs in router-LSAs.

Appendix B.  Architectural Constants

   Architectural constants for the OSPF protocol are defined in Appendix
   B of [OSPFV2].  The only difference for OSPF for IPv6 is that
   DefaultDestination is encoded as a prefix with length 0 (see
   Appendix A.4.1).

Appendix C.  Configurable Constants

   The OSPF protocol has quite a few configurable parameters.  These
   parameters are listed below.  They are grouped into general
   functional categories (area parameters, interface parameters, etc.).
   Sample values are given for some of the parameters.

   Some parameter settings need to be consistent among groups of
   routers.  For example, all routers in an area must agree on that
   area's parameters.  Similarly, all routers attached to a network must
   agree on that network's HelloInterval and RouterDeadInterval.

   Some parameters may be determined by router algorithms outside of
   this specification (e.g., the address of a host connected to the
   router via a SLIP line).  From OSPF's point of view, these items are
   still configurable.

C.1.  Global Parameters

   In general, a separate copy of the OSPF protocol is run for each
   area.  Because of this, most configuration parameters are defined on
   a per-area basis.  The few global configuration parameters are listed
   below.

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   Router ID
      This is a 32-bit number that uniquely identifies the router in the
      Autonomous System.  If a router's OSPF Router ID is changed, the
      router's OSPF software should be restarted before the new Router
      ID takes effect.  Before restarting due to a Router ID change, the
      router should flush its self-originated LSAs from the routing
      domain (see Section 14.1 of [OSPFV2]).  Otherwise, they will
      persist for up to MaxAge seconds.

   Because the size of the Router ID is smaller than an IPv6 address, it
   cannot be set to one of the router's IPv6 addresses (as is commonly
   done for IPv4).  Possible Router ID assignment procedures for IPv6
   include: a) assign the IPv6 Router ID as one of the router's IPv4
   addresses or b) assign IPv6 Router IDs through some local
   administrative procedure (similar to procedures used by manufacturers
   to assign product serial numbers).

   The Router ID of 0.0.0.0 is reserved and SHOULD NOT be used.

C.2.  Area Parameters

   All routers belonging to an area must agree on that area's
   configuration.  Disagreements between two routers will lead to an
   inability for adjacencies to form between them, with a resulting
   hindrance to the flow of both routing protocol information and data
   traffic.  The following items must be configured for an area:

   Area ID
      This is a 32-bit number that identifies the area.  The Area ID of
      0 is reserved for the backbone.

   List of address ranges
      Address ranges control the advertisement of routes across area
      boundaries.  Each address range consists of the following items:

      [IPv6 prefix, prefix length]
         Describes the collection of IPv6 addresses contained in the
         address range.

      Status
         Set to either Advertise or DoNotAdvertise.  Routing information
         is condensed at area boundaries.  External to the area, at most
         a single route is advertised (via a inter-area-prefix-LSA) for
         each address range.  The route is advertised if and only if the
         address range's Status is set to Advertise.  Unadvertised
         ranges allow the existence of certain networks to be
         intentionally hidden from other areas.  Status is set to
         Advertise by default.

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   ExternalRoutingCapability
      Whether AS-external-LSAs will be flooded into/throughout the area.
      If AS-external-LSAs are excluded from the area, the area is called
      a stub area or NSSA.  Internal to stub areas, routing to external
      destinations will be based solely on a default inter-area route.
      The backbone cannot be configured as a stub or NSSA area.  Also,
      virtual links cannot be configured through stub or NSSA areas.
      For more information, see Section 3.6 of [OSPFV2] and [NSSA].

   StubDefaultCost
      If the area has been configured as a stub area, and the router
      itself is an area border router, then the StubDefaultCost
      indicates the cost of the default inter-area-prefix-LSA that the
      router should advertise into the area.  See Section 12.4.3.1 of
      [OSPFV2] for more information.

   NSSATranslatorRole and TranslatorStabilityInterval
      These area parameters are described in Appendix D of [NSSA].
      Additionally, an NSSA Area Border Router (ABR) is also required to
      allow configuration of whether or not an NSSA default route is
      advertised in an NSSA-LSA.  If advertised, its metric and metric
      type are configurable.  These requirements are also described in
      Appendix D of [NSSA].

   ImportSummaries
      When set to enabled, prefixes external to the area are imported
      into the area via the advertisement of inter-area-prefix-LSAs.
      When set to disabled, inter-area routes are not imported into the
      area.  The default setting is enabled.  This parameter is only
      valid for stub or NSSA areas.

C.3.  Router Interface Parameters

   Some of the configurable router interface parameters (such as Area
   ID, HelloInterval, and RouterDeadInterval) actually imply properties
   of the attached links.  Therefore, these parameters must be
   consistent across all the routers attached to that link.  The
   parameters that must be configured for a router interface are:

   IPv6 link-local address
      The IPv6 link-local address associated with this interface.  May
      be learned through auto-configuration.

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   Area ID
      The OSPF area to which the attached link belongs.

   Instance ID
      The OSPF protocol instance associated with this OSPF interface.
      Defaults to 0.

   Interface ID
      32-bit number uniquely identifying this interface among the
      collection of this router's interfaces.  For example, in some
      implementations it may be possible to use the MIB-II IfIndex
      ([INTFMIB]).

   IPv6 prefixes
      The list of IPv6 prefixes to associate with the link.  These will
      be advertised in intra-area-prefix-LSAs.

   Interface output cost(s)
      The cost of sending a packet on the interface, expressed in the
      link-state metric.  This is advertised as the link cost for this
      interface in the router's router-LSA.  The interface output cost
      MUST always be greater than 0.

   RxmtInterval
      The number of seconds between LSA retransmissions for adjacencies
      belonging to this interface.  Also used when retransmitting
      Database Description and Link State Request packets.  This should
      be well over the expected round-trip delay between any two routers
      on the attached link.  The setting of this value should be
      conservative or needless retransmissions will result.  Sample
      value for a local area network: 5 seconds.

   InfTransDelay
      The estimated number of seconds it takes to transmit a Link State
      Update packet over this interface.  LSAs contained in the update
      packet must have their age incremented by this amount before
      transmission.  This value should take into account the
      transmission and propagation delays of the interface.  It MUST be
      greater than 0.  Sample value for a local area network: 1 second.

   Router Priority
      An 8-bit unsigned integer.  When two routers attached to a network
      both attempt to become the Designated Router, the one with the
      highest Router Priority takes precedence.  If there is still a
      tie, the router with the highest Router ID takes precedence.  A
      router whose Router Priority is set to 0 is ineligible to become
      the Designated Router on the attached link.  Router Priority is
      only configured for interfaces to broadcast and NBMA networks.

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   HelloInterval
      The length of time, in seconds, between Hello packets that the
      router sends on the interface.  This value is advertised in the
      router's Hello packets.  It MUST be the same for all routers
      attached to a common link.  The smaller the HelloInterval, the
      faster topological changes will be detected.  However, more OSPF
      routing protocol traffic will ensue.  Sample value for a X.25 PDN:
      30 seconds.  Sample value for a local area network (LAN): 10
      seconds.

   RouterDeadInterval
      After ceasing to hear a router's Hello packets, the number of
      seconds before its neighbors declare the router down.  This is
      also advertised in the router's Hello packets in their
      RouterDeadInterval field.  This should be some multiple of the
      HelloInterval (e.g., 4).  This value again MUST be the same for
      all routers attached to a common link.

   LinkLSASuppression
      Indicates whether or not origination of a link-LSA is suppressed.
      If set to "enabled" and the interface type is not broadcast or
      NBMA, the router will not originate a link-LSA for the link.  This
      implies that other routers on the link will ascertain the router's
      next-hop address using a mechanism other than the link-LSA (see
      Section 4.8.2).  The default value is "disabled" for interface
      types described in this specification.  It is implicitly
      "disabled" if the interface type is broadcast or NBMA.  Future
      interface types MAY specify a different default.

C.4.  Virtual Link Parameters

   Virtual links are used to restore/increase connectivity of the
   backbone.  Virtual links may be configured between any pair of area
   border routers having interfaces to a common (non-backbone) area.
   The virtual link appears as a point-to-point link with no global IPv6
   addresses in the graph for the backbone.  The virtual link must be
   configured in both of the area border routers.

   A virtual link appears in router-LSAs (for the backbone) as if it
   were a separate router interface to the backbone.  As such, it has
   most of the parameters associated with a router interface (see
   Appendix C.3).  Virtual links do not have link-local addresses, but
   instead use one of the router's global-scope IPv6 addresses as the IP
   source in OSPF protocol packets it sends on the virtual link.  Router
   Priority is not used on virtual links.  Interface output cost is not
   configured on virtual links, but is dynamically set to be the cost of
   the transit area intra-area path between the two endpoint routers.
   The parameter RxmtInterval may be configured and should be well over

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   the expected round-trip delay between the two routers.  This may be
   hard to estimate for a virtual link; it is better to err on the side
   of making it too long.

   A virtual link is defined by the following two configurable
   parameters: the Router ID of the virtual link's other endpoint and
   the (non-backbone) area that the virtual link traverses (referred to
   as the virtual link's transit area).  Virtual links cannot be
   configured through stub or NSSA areas.  Additionally, an Instance ID
   may be configured for virtual links from different protocol instances
   in order to utilize the same transit area (without requiring
   different Router IDs for demultiplexing).

C.5.  NBMA Network Parameters

   OSPF treats an NBMA network much like it treats a broadcast network.
   Since there may be many routers attached to the network, a Designated
   Router is selected for the network.  This Designated Router then
   originates a network-LSA listing all routers attached to the NBMA
   network.

   However, due to the lack of broadcast capabilities, it may be
   necessary to use configuration parameters in the Designated Router
   selection.  These parameters will only need to be configured in those
   routers that are themselves eligible to become the Designated Router
   (i.e., those routers whose Router Priority for the network is non-
   zero), and then only if no automatic procedure for discovering
   neighbors exists:

   List of all other attached routers
      The list of all other routers attached to the NBMA network.  Each
      router is configured with its Router ID and IPv6 link-local
      address on the network.  Also, for each router listed, that
      router's eligibility to become the Designated Router must be
      defined.  When an interface to an NBMA network first comes up, the
      router only sends Hello packets to those neighbors eligible to
      become the Designated Router until such time that a Designated
      Router is elected.

   PollInterval
      If a neighboring router has become inactive (Hello packets have
      not been seen for RouterDeadInterval seconds), it may still be
      necessary to send Hello packets to the dead neighbor.  These Hello
      packets will be sent at the reduced rate PollInterval, which
      should be much larger than HelloInterval.  Sample value for a PDN
      X.25 network: 2 minutes.

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C.6.  Point-to-Multipoint Network Parameters

   On point-to-multipoint networks, it may be necessary to configure the
   set of neighbors that are directly reachable over the point-to-
   multipoint network.  Each neighbor is configured with its Router ID
   and IPv6 link-local address on the network.  Designated Routers are
   not elected on point-to-multipoint networks, so the Designated Router
   eligibility of configured neighbors is not defined.

C.7.  Host Route Parameters

   Host prefixes are advertised in intra-area-prefix-LSAs.  They
   indicate either local router addresses, router interfaces to point-
   to-point networks, looped router interfaces, or IPv6 hosts that are
   directly connected to the router (e.g., via a PPP connection).  For
   each host directly connected to the router, the following items must
   be configured:

   Host IPv6 prefix
      An IPv6 prefix belonging to the directly connected host.  This
      must not be a valid IPv6 global prefix.

   Cost of link to host
      The cost of sending a packet to the host, in terms of the link-
      state metric.  However, since the host probably has only a single
      connection to the Internet, the actual configured cost(s) in many
      cases is unimportant (i.e., will have no effect on routing).

   Area ID
      The OSPF area to which the host's prefix belongs.

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Authors' Addresses

   Rob Coltun
   Acoustra Productions
   3204 Brooklawn Terrace
   Chevy Chase, MD  20815
   USA


   Dennis Ferguson
   Juniper Networks
   1194 N. Mathilda Avenue
   Sunnyvale, CA  94089
   USA

   EMail: dennis@juniper.net


   John Moy
   Sycamore Networks, Inc
   10 Elizabeth Drive
   Chelmsford, MA  01824
   USA

   EMail: jmoy@sycamorenet.com


   Acee Lindem (editor)
   Redback Networks
   102 Carric Bend Court
   Cary, NC  27519
   USA

   EMail: acee@redback.com

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Full Copyright Statement

   Copyright (C) The IETF Trust (2008).

   This document is subject to the rights, licenses and restrictions
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