1
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So wrote a four show IP interface brief.

2
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Can we ping router three?

3
00:00:08,370 --> 00:00:11,760
Yes, we can show ip ospf interface.

4
00:00:13,110 --> 00:00:19,080
OSPF is enabled on gigabit zero zero as well as the loopback interface.

5
00:00:19,320 --> 00:00:21,030
So that looks good.

6
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Are there any other problems?

7
00:00:23,010 --> 00:00:24,060
It doesn't look like it.

8
00:00:24,060 --> 00:00:33,090
So let's see if this is a problem with packet tracer or a problem with OSPF.

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Interfaces configured in area two.

10
00:00:37,740 --> 00:00:41,850
Let's have a look on the side show run.

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Interface is configured in area to.

12
00:00:47,760 --> 00:00:55,710
So what I'll do here is shut gigabit zero zero down and then no, shut it.

13
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Interfaces come up, show IP OSPF neighbor.

14
00:01:01,800 --> 00:01:05,459
We've got a neighbor relationship currently to router to.

15
00:01:06,120 --> 00:01:10,860
Hopefully after a while we'll have a neighbor relationship.

16
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To tend on 1.3.2, which is root of four.

17
00:01:16,490 --> 00:01:18,950
We can ping that IP address.

18
00:01:21,030 --> 00:01:29,220
Sometimes I find that in packet tracer, even though everything is configured right, you may have problems.

19
00:01:30,240 --> 00:01:34,770
So here is another issue that I've encountered with Packet Tracer.

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Notice this command is now missing from this interface.

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So interface gigabit zero, slash zero.

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I'll paste that command back.

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So show IP OSPF interface.

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00:01:54,240 --> 00:01:57,240
OSPF is configured on the loopback interface.

25
00:01:57,720 --> 00:02:01,140
It's configured on the gigabit zero zero interface.

26
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Show IP OSPF neighbor.

27
00:02:04,680 --> 00:02:08,910
Hopefully we should see a neighbor relationship come up.

28
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But if that doesn't work, what I'm going to do is use the network command rather than the interface

29
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command to kick start OSPF.

30
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So rather ospf one network.

31
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And I'll enable OSPF on all interfaces in Area two.

32
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At the moment we still don't see a neighbor relationship here.

33
00:02:37,690 --> 00:02:39,910
So when I enter that command.

34
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Show IP OSPF neighbor.

35
00:02:44,660 --> 00:02:48,590
Hopefully our OSPF neighbor relationship should come up.

36
00:02:48,950 --> 00:02:51,830
Let's check if the same thing happened on the side.

37
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Yes.

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Notice the command was removed from this interface.

39
00:02:56,330 --> 00:02:58,790
So let's put that back.

40
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So interface gigabit.

41
00:03:01,890 --> 00:03:02,910
Zero zero.

42
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I'll paste that back.

43
00:03:06,630 --> 00:03:10,050
And as you can see now, the relationship has now come up again.

44
00:03:10,970 --> 00:03:13,040
So show ip ospf neighbor.

45
00:03:13,220 --> 00:03:18,170
We have a neighbor relationship and we can ping the loopback of router for.

46
00:03:20,880 --> 00:03:25,080
On Route one, we can ping the loopback of router four.

47
00:03:25,470 --> 00:03:32,070
So for the real world, this shouldn't happen where commands are suddenly removed.

48
00:03:32,250 --> 00:03:35,130
But that may happen in packet tracer.

49
00:03:37,000 --> 00:03:44,830
It's a good lesson to learn, though, that when you make a change, just recheck things to verify that

50
00:03:44,830 --> 00:03:47,710
things are still the way that you think they are.

51
00:03:48,100 --> 00:03:51,880
So in this example, OSPF commands had been removed.

52
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So ip ospf neighbor notice the neighbor relationship is now good.

53
00:04:00,200 --> 00:04:02,930
So let me show you this on a real router.

54
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This is a physical rudder running locally.

55
00:04:10,520 --> 00:04:12,600
It's a 1941 router show.

56
00:04:12,620 --> 00:04:20,240
IP Interface brief shows me a number of interfaces, including gigabit or zero one.

57
00:04:20,240 --> 00:04:23,120
So show run interface gigabit is error one.

58
00:04:23,750 --> 00:04:30,920
OSPF is not currently enabled on that interface, but if I go on to that interface and I type IP OSPF

59
00:04:30,920 --> 00:04:42,710
one area to show run interface gigabit 0/1 notice OSPF is enabled on the interface in area two.

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00:04:44,060 --> 00:04:52,460
If I shut that interface down and do the show run again, notice the command is not removed even though

61
00:04:52,460 --> 00:05:01,250
the interface has shut down packet trace added to that which is not correct when compared to a real

62
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Cisco router.

63
00:05:03,980 --> 00:05:07,910
Packet trace is fantastic software, but it's not perfect.

64
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It's a simulator, so sometimes things don't work exactly as they would work on a real physical router.

65
00:05:16,340 --> 00:05:20,780
But for this lab, we've been able to solve the problem.

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Rather, one is learning about the loopback of router four and is able to ping the loopback of router

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four.

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I hope you found that useful and that you've learned some troubleshooting tips for the real world.