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3.12. OSPF External Link State Database

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3.12. OSPF External Link State Database

3.12. OSPF External Link State Database

--  OSPF Link State Database, External

--      The Link State Database contains the Link State
--      Advertisements from throughout the areas that the
--      device is attached to.

--             This table is identical to the OSPF LSDB Table in
--      format, but contains only External Link State
--             Advertisements.  The purpose is to allow external
--      LSAs to be displayed once for the router rather
--      than once in each non-stub area.

    ospfExtLsdbTable OBJECT-TYPE
        SYNTAX   SEQUENCE OF OspfExtLsdbEntry
        MAX-ACCESS   not-accessible
        STATUS   current
        DESCRIPTION
           "The OSPF Process's Links State Database."
       REFERENCE
          "OSPF Version 2, Section 12  Link  State  Adver-
          tisements"
      ::= { ospf 12 }


    ospfExtLsdbEntry OBJECT-TYPE
        SYNTAX   OspfExtLsdbEntry
        MAX-ACCESS   not-accessible
        STATUS   current
        DESCRIPTION
           "A single Link State Advertisement."
       INDEX { ospfExtLsdbType, ospfExtLsdbLsid, ospfExtLsdbRouterId }
       ::= { ospfExtLsdbTable 1 }

OspfExtLsdbEntry ::=
    SEQUENCE {
        ospfExtLsdbType
            INTEGER,
        ospfExtLsdbLsid
            IpAddress,
        ospfExtLsdbRouterId
            RouterID,
        ospfExtLsdbSequence
            Integer32,
        ospfExtLsdbAge
            Integer32,
        ospfExtLsdbChecksum
            Integer32,
        ospfExtLsdbAdvertisement
            OCTET STRING
              }

    ospfExtLsdbType OBJECT-TYPE
        SYNTAX   INTEGER    {
                    asExternalLink (5)
                  }
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "The type  of  the  link  state  advertisement.
           Each  link state type has a separate advertise-
           ment format."
       REFERENCE
          "OSPF Version 2, Appendix A.4.1 The  Link  State
          Advertisement header"
      ::= { ospfExtLsdbEntry 1 }


    ospfExtLsdbLsid OBJECT-TYPE
        SYNTAX   IpAddress
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "The Link State ID is an LS Type Specific field
           containing either a Router ID or an IP Address;
           it identifies the piece of the  routing  domain
           that is being described by the advertisement."
       REFERENCE
          "OSPF Version 2, Section 12.1.4 Link State ID"
      ::= { ospfExtLsdbEntry 2 }


    ospfExtLsdbRouterId OBJECT-TYPE
        SYNTAX   RouterID
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "The 32 bit number that uniquely identifies the
           originating router in the Autonomous System."
       REFERENCE
          "OSPF Version 2, Appendix C.1 Global parameters"
      ::= { ospfExtLsdbEntry 3 }

--  Note that the OSPF Sequence Number is a 32 bit signed
--  integer.  It starts with the value '80000001'h,
--  or -'7FFFFFFF'h, and increments until '7FFFFFFF'h
--  Thus, a typical sequence number will be very negative.
    ospfExtLsdbSequence OBJECT-TYPE
        SYNTAX   Integer32
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "The sequence number field is a  signed  32-bit
           integer.   It  is used to detect old and dupli-
           cate link state advertisements.  The  space  of
           sequence  numbers  is  linearly  ordered.   The
           larger the sequence number the more recent  the
           advertisement."
       REFERENCE
          "OSPF Version  2,  Section  12.1.6  LS  sequence
          number"
      ::= { ospfExtLsdbEntry 4 }


    ospfExtLsdbAge OBJECT-TYPE
        SYNTAX   Integer32    -- Should be 0..MaxAge
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "This field is the age of the link state adver-
           tisement in seconds."
       REFERENCE
          "OSPF Version 2, Section 12.1.1 LS age"
      ::= { ospfExtLsdbEntry 5 }


    ospfExtLsdbChecksum OBJECT-TYPE
        SYNTAX   Integer32
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "This field is the  checksum  of  the  complete
           contents  of  the  advertisement, excepting the
           age field.  The age field is excepted  so  that
           an   advertisement's  age  can  be  incremented
           without updating the  checksum.   The  checksum
           used  is  the same that is used for ISO connec-
           tionless datagrams; it is commonly referred  to
           as the Fletcher checksum."
       REFERENCE
          "OSPF Version 2, Section 12.1.7 LS checksum"
      ::= { ospfExtLsdbEntry 6 }


    ospfExtLsdbAdvertisement OBJECT-TYPE
        SYNTAX   OCTET STRING (SIZE(36))
        MAX-ACCESS   read-only
        STATUS   current
        DESCRIPTION
           "The entire Link State Advertisement, including
           its header."
       REFERENCE
          "OSPF Version 2, Section 12  Link  State  Adver-
          tisements"
      ::= { ospfExtLsdbEntry 7 }



Next: 3.13. OSPF Route Table Use

Connected: An Internet Encyclopedia
3.12. OSPF External Link State Database