Neighbors; Adjacency - Cisco Nexus 7000 Series Configuration Manual

Chapter 7 Configuring OSPFv3
S e n d d o c u m e n t c o m m e n t s t o n e x u s 7 k - d o c f e e d b a c k @ c i s c o . c o m .
Hello packets also include a list of router IDs for the routers that the originating interface has
communicated with. If the receiving interface sees its own router ID in this list, then bidirectional
communication has been established between the two interfaces.
OSPFv3 uses Hello packets as a keepalive message to determine if a neighbor is still communicating. If
a router does not receive a Hello packet by the configured
interval), then the neighbor is removed from the local neighbor table.

Neighbors

An OSPFv3 interface must have a compatible configuration with a remote interface before the two can
be considered neighbors. The two OSPFv3 interfaces must match the following criteria:
•
•
•
•
If there is a match, the information is entered into the neighbor table:
•
•
•
•
•
•
•
When the first Hello packet is received from a new neighbor, the neighbor is entered into the neighbor
table in the init state. Once bidirectional communication is established, the neighbor state becomes
2-way. ExStart and exchange states come next, as the two interfaces exchange their link-state database.
Once this is all complete, the neighbor moves into the full state, signifying full adjacency. If the neighbor
fails to send any Hello packets in the dead interval, then the neighbor is moved to the down state and is
no longer considered adjacent.

Adjacency

Not all neighbors establish adjacency. Depending on the network type and designated router
establishment, some neighbors become fully adjacent and share LSAs with all their neighbors, while
other neighbors do not. For more information, see the
Adjacency is established using Database Description packets, Link State Request packets, and Link
State Update packets in OSPFv3. The Database Description packet includes just the LSA headers from
the link-state database of the neighbor (see the
router compares these headers with its own link-state database and determines which LSAs are new or
OL-20002-02
Hello interval
Dead interval
Area ID (see the "Areas" section on page
Optional capabilities
Neighbor ID—The router ID of the neighbor router.
Priority—Priority of the neighbor router. The priority is used for designated router election (see the
"Designated Routers" section on page
State—Indication of whether the neighbor has just been heard from, is in the process of setting up
bidirectional communications, is sharing the link-state information, or has achieved full adjacency.
Dead time—Indication of how long since the last Hello packet was received from this neighbor.
Link-local IPv6 Address—The link-local IPv6 address of the neighbor.
Designated Router—Indication of whether the neighbor has been declared the designated router or
backup designated router (see the
Local interface—The local interface that received the Hello packet for this neighbor.
Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
dead interval
7-5)
7-4).
"Designated Routers" section on page
"Designated Routers" section on page
"Link-State Database" section on page
Information About OSPFv3
(usually a multiple of the hello
7-4).
7-4.
7-7). The local
7-3