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Okay.

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So here's the shot capture I faulted for OSPF.

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We've got our two routers once again, this is rather one.

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This is router two.

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This is not an easy one to work out.

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Let me start with rather two.

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So if we look at right a T, we can see hello packet, we can see router ID, we can see and I'll just

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move this up.

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We can see password.

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There's the password.

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In the OSPF packet, we can see the subnet mask.

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We don't see designated router backup designated router in the output.

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We see data block.

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Not too much here.

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Extended twelves don't see too much.

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That's interesting.

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Let's see if we can see a difference on router one.

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So router one backbone area and that's what's this is what's nice.

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You can jump from one router to the other.

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So this is rather one.

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This is router two that looks right.

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Simple password, right of one, router two that looks the same.

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Authentication.

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Same password.

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Subnet mask looks the same.

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Hello?

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Interval.

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Okay, here's something different.

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Notice.

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Hello.

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Intervals.

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10 seconds.

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Hello.

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Interval.

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Here is 30 seconds.

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If we look at.

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Did interval date interval be 120 seconds.

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The other right is 40 seconds.

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Now, this is something in OSPF as well that you need to be careful of.

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If the hollow interval is different, they're not going to form a neighbor relationship.

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That interval is different.

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They're not going to form a neighbor relationship.

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If the two routers don't form a neighbor relationship, they won't exchange routes with one another

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and routing will be broken.

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If we have a look through the output here, we don't see any exchange of messages.

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We only see hollow packets.

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They will never form a neighbor relationship because the intervals are different.

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So what I'll do is run the Wireshark capture again so you can see this in real time while I'm fixing

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it.

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So what we'll search for is OSPF we see both the routers advertising and if we look in the packet notice

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we see a difference between hollow interval on the one router and the other router.

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So router one has a 32nd hollow interval.

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Router two has a 10/2 hollow interval.

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That's not right.

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Either the OSPF network type has been changed or hollow timers have been changed on the riders.

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They are not the same.

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This is Ethernet.

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They should be the same.

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So something's being changed either on the OSPF network type or.

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On the hollow and dead intervals.

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That's typically done on an interface.

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So show run.

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Interface gigabit.

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Zero one.

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Notice this option.

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Here is the problem right away.

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I know this because I've been working with OSPF for a long time.

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You may not be aware of that.

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But be careful in OSPF.

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The network type has to be the same.

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Another way to look at that is to type show IP OSPF interface.

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And let me do a specific interface.

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Okay.

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Give it zero zero.

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So show IP OSPF interface gigabit zero zero.

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That's this interface on the right.

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On the right show IP OSPF interface gigabit zero one.

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That's this interface.

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Notice what we see here.

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We don't see that on the side.

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We see priority.

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We see DRT.

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On the side.

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We don't see.

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D.R. That was another giveaway.

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So if you go back to the Wireshark capture.

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Notice.

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On the one router router, one designated router and back up designated router are set to 0000, whereas

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on the other router we have a designated rider.

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Now there's no backup designated rider because Rider two sees itself as the designated rider.

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But Rider one is not using a broadcast media.

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It's set to point to multipoint so it doesn't go through an election process.

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It doesn't take part in the election.

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So there's no backup.

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Designated Rider.

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Rider two sees itself as the designated rider.

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No backup designated rider, but rider one doesn't see either.

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That is a giveaway straight away.

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Apart from the timers, that tells you that there's a problem between these two riders now they don't

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have to both use.

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Port cos they could use point of multipoint.

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But on Ethernet you want to use broad cos that's the default mechanism used.

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You can see the network type right over there broadcast.

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You can see over here network type point to multipoint.

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They need to be the same.

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Otherwise they're not going to form a neighbor relationship.

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So show run interface gigabit zero one.

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What I would do here is type IP OSPF network.

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Notice the options.

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I'm going to select broadcast.

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So show run interface gigabit zero one again.

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Notice Network is broadcast over there.

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See the black in Wireshark neighbor relationship has been formed and the routers are starting to advertise

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routes to one another.

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So we know this is working just through the Wireshark captures.

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But you can also see that on the consoles of the routers.

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Notice neighbor relationships are formed to show IP.

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OSPF Neighbor neighbor relationship is established between those two routers known as full BTR.

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In other words, router one is the backup designated router on this side.

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Show IP ospf neighbor.

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Rather two is the designated rider.

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This is looking at it from router one's point of view.

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Show IP route routes have been advertised.

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They are shown in the routing table.

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So on the two PCs, they can now ping one another.

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We've successfully resolved this network issue.

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The hint or the thing to look out for was notice designated right.

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A backup designator auto was zeros and the timers were different.

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So if we scroll down to when the change was made notice, we see the timers as 10/2 on the one and 10/2

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on the other.

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It doesn't show us the designated backup designated order yet because it's still going through that

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election.

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But after a while we should see that notice.

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D.

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R btr.

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Once they successfully elected and told each other about one another.

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And then they.

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Exchange rates with each other.

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Okay, so I'll save this Wireshark capture.

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I'll stop it here and then I'll save it as OSPF.

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RT Is three fixed, so if you want to see what it actually looks like once it's working, there you

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go.

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Okay, so how are you doing with these troubleshooting videos and laps?

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It's not that easy, but it's a real test of your networking knowledge and whether you can analyze packets

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properly.