State:
The state of the neighbor:
Down: This is the initial state of a neighbor conversation.
It indicates that there has been no recent information
received from the neighbor. On NBMA networks, Hello
packets may still be sent to 'Down' neighbors, although
at a reduced frequency.
Attempt: 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 Hello Interval.
Init: In this state, a 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
greater) are listed in the Hello packets sent from the
associated interface.
2-Way: 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.
ExStart: 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.
Exchange: In this state the router is describing its entire
link state database by sending Database Description
packets to the neighbor. 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. These adjacencies are fully capable of
transmitting and receiving all types of OSPF routing
protocol packets.
Loading: 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.
Full: In this state, the neighboring routers are fully
adjacent. These adjacencies will now appear in Router
LSAs and Network LSAs.
Events:
The number of times this neighbor relationship has changed
state, or an error has occurred.
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