Time
30 hours 46 minutes
Difficulty
Intermediate
CEU/CPE
20

Video Description

OSPF Neighbor States This lesson is an excellent demonstration of how OSPF works between neighboring devices. We begin by exploring all the fields in the Hello Packet and examining them in detail covering the CCNA exam and what you should know as a practicing CCNA. You'll learn where in the sharing process routers become OSPF neighbors and start the database information sharing. We'll also examine what's met by the "Down" state and how that is different from FULL and what takes place during each of these states.

Video Transcription

00:04
So before I continue, we shouldn't discuss all the fields in the hello packets that you should memorize. And no,
00:12
And these fields are
00:14
the router. I d. Hello, Packet contains the router I d off the router originating the hello
00:21
the Hello and dead timers. The hello timer being
00:25
the timer. How often I send hellos and the debt timer being How long should I wait
00:31
to hear from a neighboring router before considering it down So before considering it dead. So how long a neighboring router should wait for me to send another hello before considering me down
00:45
all your neighbors Router ID's.
00:48
Which means all my neighboring routers, their outer ideas will be contained in hello messages that I am sending
00:56
the area i d of the originating interface. This won't make sense right now. It will make sense in a little bit for oh, SPF breaks down
01:03
a large network and two smaller, easier to maintain areas. And these areas have an area i d. As we get to our lab, this will make more sense.
01:14
The router priority the SPF for our priority which remember I said by default is one, and it can range between zero and 255 The router with the highest priority becomes the D. R
01:26
the D R I P address or the designated route or i p address the backup designated route or I p address and any attending Gatien information if present.
01:38
Now,
01:38
after two routers exchange hellos with all this information, they become neighbors once they become neighbors. This start they did a basic change or link state database exchange. And this exchange happens in 12345678 steps, while seven steps
01:57
last ones
01:59
when it ends.
02:00
So two neighbors start to SPF. Neighbors start in the down state. This doesn't mean that the router is down. It just means they start in a state call the downstate.
02:12
So in the downstate, a router has
02:15
received Ah, hello
02:16
from the opposite end,
02:20
then the routers transition to the attempt state. Now the attempt state is only seen in non broadcast multi access networks like frame relay, which will we retrieval tackle later.
02:32
So in that time, state neighbors must be configured manually with the neighbour command.
02:39
However, oh, SPF over frame really is not part of C C N A. But I will attempt to show you the neighbor command.
02:47
Next we move on to the in its state in it state which says, Which means that the hollow packet has been received from the opposite side or from a neighboring this device.
03:01
Next we move on to the two way state. And this day it means that I have received a hello packet from my neighbor with my own router. I d in that Hello. Which means that bi directional communication has been established.
03:16
Next, routers move on to the Ex start state, where routers prepare for links. Did database
03:24
synchronization by exchanging packets called the Universe description packets
03:30
the router with the highest router I D amongst all becomes the master router and controls the database exchange with the other routers.
03:39
Then you move on to the exchange state in the exchange state did of his description or Dede packets Ling state requests, packets and links that abed packets
03:52
are used to exchange the link state database between two routers or two or more routers in the loading state links. Did request packets ascent requesting missing link state advertisements or l essays that I might have missed from you that you might have in your link state database, but haven't sent to me yet.
04:11
This links did request packets or these links state requests Packets are responded to by Ling State. A big packets containing these essays.
04:21
Once this exchange is completely done and the two routers databases are completely synchronized. You move on to the full adjacency or you have fully exchanged your databases with each other. So you are in the full state.
04:38
This ends
04:39
the neighbor state machine lecture.

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Cisco Certified Network Associate (CCNA) Certification

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Instructed By

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Junaid Memon
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