network cisco ccna gns3 certification arteq

network cisco ccna gns3 certification arteq
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Monday, November 19, 2012

ospf states...

according to rfc 2328... (abridged)

            This is the initial state of a neighbor conversation.  It
            indicates that there has been no recent information received
            from the neighbor.
            This state is only valid for neighbors attached to NBMA
            networks.  It indicates that no recent information has been
            received from the neighbor, but that a more concerted effort
            should be made to contact the neighbor.  This is done by
            sending the neighbor Hello packets at intervals of
            In this state, an Hello packet has recently been seen from
            the neighbor.  However, bidirectional communication has not
            yet been established with the neighbor (i.e., the router
            itself did not appear in the neighbor's Hello packet).  All
            neighbors in this state (or higher) are listed in the Hello
            packets sent from the associated interface. 

            In this state, communication between the two routers is
            bidirectional.  This has been assured by the operation of
            the Hello Protocol.  This is the most advanced state short
            of beginning adjacency establishment.  The (Backup)
            Designated Router is selected from the set of neighbors in
            state 2-Way or greater.

            This is the first step in creating an adjacency between the
            two neighboring routers.  The goal of this step is to decide
            which router is the master, and to decide upon the initial
            DD sequence number.  Neighbor conversations in this state or
            greater are called adjacencies.

            In this state the router is describing its entire link state
            database by sending Database Description packets to the
            neighbor.  Each Database Description Packet has a DD
            sequence number, and is explicitly acknowledged.  Only one
            Database Description Packet is allowed outstanding at any
            one time.  In this state, Link State Request Packets may
            also be sent asking for the neighbor's more recent LSAs.
            All adjacencies in Exchange state or greater are used by the
            flooding procedure.  In fact, these adjacencies are fully
            capable of transmitting and receiving all types of OSPF
            routing protocol packets.

            In this state, Link State Request packets are sent to the
            neighbor asking for the more recent LSAs that have been
            discovered (but not yet received) in the Exchange state.

            In this state, the neighboring routers are fully adjacent.
            These adjacencies will now appear in router-LSAs and
  This state designates that bi-directional communication has been
  established between two routers. Bi-directional means that each router has seen
  the other's hello packet. This state is attained when the router receiving the
  hello packet sees its own Router ID within the received hello packet's neighbor
  field. At this state, a router decides whether to become adjacent with this
  neighbor. On broadcast media and non-broadcast multiaccess networks, a router
  becomes full only with the designated router (DR) and the backup designated router
  (BDR); it stays in the 2-way state with all  other neighbors. On Point-to-point and
   Point-to-multipoint networks, a router becomes full with all connected routers.
 At the end of this stage, the DR and BDR for broadcast and
  non-broadcast multiacess networks are elected. For more information on the DR
  election process, refer to DR   Election.

Note: Receiving a Database Descriptor (DBD) packet from a neighbor in the
  init state will also a cause a transition to 2-way state.

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