1
00:00:08,960 --> 00:00:14,550
This is one of multiple Ethernet trouble shooting videos in this typology.

2
00:00:14,560 --> 00:00:20,870
We've been told that to write one on the top left is not able to ping some of the other routers in the

3
00:00:20,870 --> 00:00:29,840
topology so let's verify that on right of one show IP interface brief IP address of Rodda one is 10

4
00:00:29,840 --> 00:00:40,750
to 1 and 1 to one to IP address is 10 1 to 1 and 2.

5
00:00:40,790 --> 00:00:50,640
So from Router one can be paying Rodda to pings or failing Let's confirm the IP address information

6
00:00:50,650 --> 00:00:58,340
so show IP interface gigabit 0 0 IP addresses 10 1 1 to slice 24.

7
00:00:58,760 --> 00:00:59,870
Let's do the same over here.

8
00:00:59,870 --> 00:01:09,950
Make sure that the subnet mask is correct IP address is 10 1 1 1 slice 24 the side it's 10 1 1 2 slice

9
00:01:09,950 --> 00:01:10,790
24.

10
00:01:11,030 --> 00:01:12,620
So that looks good.

11
00:01:13,640 --> 00:01:19,620
Doesn't look like they'll be any other reason why we can't ping to rot it too.

12
00:01:20,210 --> 00:01:23,160
What we'll do is do a debug IP packet.

13
00:01:23,330 --> 00:01:27,310
Be careful doing these commands in the real world.

14
00:01:27,920 --> 00:01:31,700
You may have to use an access list on that debug.

15
00:01:32,030 --> 00:01:37,100
Otherwise you could kill your Rodda with the amount of output that's generated.

16
00:01:37,100 --> 00:01:42,100
OK so we see messages such as sending full packet.

17
00:01:42,530 --> 00:01:51,680
So it looks like Rato one is forcing the packet out of the net interface onto the network to debug IP

18
00:01:51,680 --> 00:01:52,980
packet on the side.

19
00:01:54,020 --> 00:02:03,210
What I'll do now is repeat one ping only so I only send one packet onto the network.

20
00:02:03,250 --> 00:02:07,600
It doesn't look like anything's arriving on the site.

21
00:02:07,660 --> 00:02:14,980
If you can use why a shock to help you capture traffic someone to capture traffic between the switch

22
00:02:15,040 --> 00:02:23,740
and router to and to that ping again.

23
00:02:23,940 --> 00:02:29,910
But I don't see any ICMP traffic in shock.

24
00:02:32,840 --> 00:02:39,670
We see spending information but we don't see any other information in why shark we see for instance

25
00:02:39,670 --> 00:02:43,310
a loop from a device with a MAC address.

26
00:02:43,330 --> 00:02:47,550
We see some spending tree we don't see any of the traffic

27
00:02:52,410 --> 00:02:55,800
so let's see if the traffic is actually getting to the switch.

28
00:02:57,720 --> 00:02:59,360
We'll do that ping again.

29
00:02:59,710 --> 00:03:11,070
OK so this the ICMP message sent from brought a one to router to the fact that we see ICMP means that

30
00:03:11,070 --> 00:03:17,940
the router has learnt the MAC address of router to its MAC address is zeroes ending in one destination

31
00:03:17,940 --> 00:03:21,830
MAC address is zeroes ending in a two.

32
00:03:21,850 --> 00:03:23,710
So it looks like up worked.

33
00:03:23,800 --> 00:03:25,920
But the pings are failing.

34
00:03:26,200 --> 00:03:35,560
Let's confirm the MAC address on router 1 MAC address is set to this point in MAC addresses this to

35
00:03:35,600 --> 00:03:38,670
the MAC address has been changed to that value.

36
00:03:39,200 --> 00:03:46,650
What about on rodded to MAC addresses this burnt in MAC addresses that.

37
00:03:46,900 --> 00:03:53,840
So it looks like the traffic from Router one to router to get sent on this link but doesn't arrive at

38
00:03:53,870 --> 00:03:57,260
route to what I'll do is do a broadcast.

39
00:03:57,290 --> 00:04:03,240
Again you need to be careful with doing this kind of stuff in the real world.

40
00:04:05,840 --> 00:04:08,960
Because this is a lab I'm going to show you various options.

41
00:04:09,230 --> 00:04:14,340
So I notice when I send a broadcast traffic it does arrive at route too.

42
00:04:14,450 --> 00:04:22,490
So let me on all that and only do a D-bag IP ICMP not a debug package because that generates a lot of

43
00:04:22,490 --> 00:04:27,010
traffic on all over here.

44
00:04:28,560 --> 00:04:33,730
In other words turn off all debugging and only send one broadcast.

45
00:04:34,140 --> 00:04:44,280
So the broadcast gets to rodded to say here we got a reply to the broadcast it looks like but it doesn't

46
00:04:44,280 --> 00:04:48,160
look like unicast traffic works in the network.

47
00:04:49,620 --> 00:04:54,500
So broadcast he sent it gets to write it too.

48
00:04:54,900 --> 00:05:00,050
But a unique cost doesn't seem to get to rodded too.

49
00:05:00,420 --> 00:05:03,780
So let's have a look at that switch and see if there's a problem on the switch.

50
00:05:05,920 --> 00:05:09,900
So on the switch shows mac address table.

51
00:05:10,280 --> 00:05:10,610
OK.

52
00:05:10,610 --> 00:05:19,060
Can you see a problem in the output what looks wrong in the output.

53
00:05:19,120 --> 00:05:25,760
Now this year we've got a static MAC address for MAC address to going out of gigabit.

54
00:05:25,800 --> 00:05:27,670
Two and Three.

55
00:05:27,970 --> 00:05:34,680
But switch to show interface gigabit.

56
00:05:34,770 --> 00:05:40,660
0 shows us that has a MAC address of two.

57
00:05:41,070 --> 00:05:49,310
So this static MAC addresses a problem show run pumping include Mac.

58
00:05:49,470 --> 00:05:53,400
We've got to this entry in the running config which shouldn't be there.

59
00:05:53,420 --> 00:05:56,190
So no I'll paste that in.

60
00:05:57,800 --> 00:06:03,120
So no MAC address show MAC Address table.

61
00:06:03,140 --> 00:06:09,900
Now we only have a dynamic MAC addresses I'll do a ping from Router one to write to that succeeds.

62
00:06:09,910 --> 00:06:13,850
No because the MAC address has been lent properly.

63
00:06:13,850 --> 00:06:20,120
Be careful with static MAC addresses in your MAC address table that will override your dynamic entries

64
00:06:20,480 --> 00:06:24,500
and could send traffic to the wrong port in your typology.

65
00:06:25,330 --> 00:06:31,400
Ok so can we ping rotas 3 which has an IP address of 10 1 1 3.

66
00:06:31,480 --> 00:06:38,680
No we can't show IP interface Gieger But 0 0.

67
00:06:38,780 --> 00:06:48,610
So this is the IP address of router 3 de-bug IP ICMP.

68
00:06:48,710 --> 00:06:51,200
Let's do a ping again.

69
00:06:52,170 --> 00:06:55,180
It doesn't look like the traffic's arriving at Rodda 3.

70
00:06:55,350 --> 00:06:57,470
Let's have a look at the MAC address table.

71
00:06:57,990 --> 00:07:07,710
I don't see a MAC address for router 3 that's paying Router one from router 3.

72
00:07:07,740 --> 00:07:11,180
Look at this output and see if you see a problem.

73
00:07:13,340 --> 00:07:20,060
So show mac address table showed us previously that the MAC address ending in one was connected to Gigabit

74
00:07:20,070 --> 00:07:22,490
to 0 0 on the switch.

75
00:07:22,490 --> 00:07:31,370
In other words over here but now it looks like that MAC addresses on gigabit 0 to this port here.

76
00:07:31,500 --> 00:07:36,160
So do ping from Router one again and let's have a look at the MAC address table.

77
00:07:36,180 --> 00:07:45,570
Notice that MAC address is now shown on gigabit 00 ping is finished so let's do to ping from the side.

78
00:07:45,570 --> 00:07:48,580
Notice the MAC address has moved to Gigabit.

79
00:07:48,580 --> 00:07:50,000
0 2.

80
00:07:50,370 --> 00:07:53,980
So we getting MAC addresses flipping on the switch.

81
00:07:54,390 --> 00:07:57,570
Let's confirm what the MAC address is on these routers.

82
00:07:57,900 --> 00:08:00,320
So show interface could give it a 0 0.

83
00:08:00,690 --> 00:08:04,040
That's the MAC address of router 1.

84
00:08:04,080 --> 00:08:05,810
What does it look like on Route 3.

85
00:08:05,850 --> 00:08:08,260
So show interface.

86
00:08:08,260 --> 00:08:14,130
Gigabit 0 0 this is the Rogers interface.

87
00:08:14,160 --> 00:08:15,530
Notice the MAC address.

88
00:08:15,780 --> 00:08:18,820
The rodders have duplicate MAC addresses.

89
00:08:18,900 --> 00:08:28,280
That's not going to work in an Ethernet environment so let's configure the MAC address as follows.

90
00:08:29,100 --> 00:08:40,420
And let's see if Rotto one can ping wrote three 3 Now notice the ping succeeds and that's because the

91
00:08:40,420 --> 00:08:45,360
devices have different MAC addresses now available on different ports.

92
00:08:45,430 --> 00:08:52,930
Which is correct Prod. diagram Ethernet breaks if you have the same MAC addresses on the same layer

93
00:08:52,960 --> 00:08:57,450
to segment MAC addresses are meant to be unique.

94
00:08:57,640 --> 00:09:04,150
But in the real world you can encounter duplicate MAC addresses check your MAC address tables to see

95
00:09:04,150 --> 00:09:07,630
if MAC addresses a flipping from one port to another.

96
00:09:07,630 --> 00:09:09,090
Hope you enjoy this video.

97
00:09:09,220 --> 00:09:15,090
If it's been of benefit to you please like it and please subscribe to my YouTube channel.

98
00:09:15,100 --> 00:09:16,780
I wish you all the very best.