1
00:00:00,000 --> 00:00:05,000
So CDP is very useful but CDP is propriety

2
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sh cdp neighbors as an example

3
00:00:08,000 --> 00:00:23,000
shows me that my local device is shown in the list of neighbors that is the local router.

4
00:00:23,000 --> 00:00:25,000
Notice the IP address of the local router

5
00:00:25,000 --> 00:00:30,000
that’s the IP address shown in the neighboring output

6
00:00:30,000 --> 00:00:35,000
and that’s typically because there is a non Cisco device in the network

7
00:00:35,000 --> 00:00:37,000
that is forwarding CDP messages.

8
00:00:37,000 --> 00:00:41,000
So the routers actually seeing itself through the network

9
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because there is a loop somewhere or there might be another problem.

10
00:00:45,000 --> 00:00:50,000
So how do I see neighboring devices that may not be using CDP?

11
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In other words non Cisco devices.

12
00:00:53,000 --> 00:00:56,000
Well, I can do that by enabling LLDP.

13
00:00:56,000 --> 00:00:58,000
Now this router doesn’t support LLDP

14
00:00:58,000 --> 00:01:05,000
but as an example, if I telnet to my 3750 switch

15
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so let’s have a look at the details

16
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here it's IP address and then I'll telnet to it.

17
00:01:11,000 --> 00:01:17,000
This switch which is a physical Cisco switch

18
00:01:17,000 --> 00:01:21,000
So this is knowledge in GNS3, switches is a physical 3750

19
00:01:21,000 --> 00:01:31,000
so we can see various physical interfaces on the switch

20
00:01:31,000 --> 00:01:33,000
this switch does support LLDP.

21
00:01:33,000 --> 00:01:41,000
Notice I can type lldp run to enable LLDP on this switch.

22
00:01:41,000 --> 00:01:43,000
So sh cdp neighbors

23
00:01:43,000 --> 00:01:46,000
shows me my Cisco devices

24
00:01:46,000 --> 00:01:49,000
but notice sh lldp neighbors

25
00:01:49,000 --> 00:01:58,000
shows me non Cisco devices including a Dell server and Ubuntu hypervisor server.

26
00:01:58,000 --> 00:02:03,000
So these are Linux based servers running in my local network.

27
00:02:03,000 --> 00:02:07,000
The Dell server has 2 connections to the switch.

28
00:02:07,000 --> 00:02:17,000
So the local 3750 is connected to the Dell on both F0/24 as well as 0/23

29
00:02:17,000 --> 00:02:22,000
the Ubuntu servers connected to F1/0/19

30
00:02:22,000 --> 00:02:28,000
let’s look at details so sh lldp neighbors detail

31
00:02:28,000 --> 00:02:34,000
I can see that this is a Dell server, it's using Ethernet 1

32
00:02:34,000 --> 00:02:42,000
to connect to the switch scrolling down

33
00:02:42,000 --> 00:02:48,000
I can see that the Dell server is connecting via Ethernet 0

34
00:02:48,000 --> 00:02:51,000
to the local switch as well.

35
00:02:51,000 --> 00:02:53,000
So the Dell server got both of its Ethernet network cards

36
00:02:53,000 --> 00:02:59,000
connected to the local 3750, I'll do that command again

37
00:02:59,000 --> 00:03:02,000
so sh lldp neighbors detail

38
00:03:02,000 --> 00:03:06,000
notice we can see the IP address of the Dell server

39
00:03:06,000 --> 00:03:09,000
we can see the operating system on the Dell server

40
00:03:09,000 --> 00:03:15,000
it's running Ubuntu 14/04, it’s an x86 64 bit operating system.

41
00:03:15,000 --> 00:03:20,000
We can see the options for physical media capabilities

42
00:03:20,000 --> 00:03:24,000
so it supports gigabit Ethernet running at full duplex.

43
00:03:24,000 --> 00:03:34,000
On this Ubuntu server it’s connected using port P2 P1

44
00:03:34,000 --> 00:03:39,000
this Ubuntu server is actually running a virtual box in Ubuntu

45
00:03:39,000 --> 00:03:45,000
and has various tag interfaces hence this interesting name of an interface.

46
00:03:45,000 --> 00:03:49,000
This is the IP address of that Ubuntu server.

47
00:03:49,000 --> 00:03:57,000
So in the same way that CDP allows me to see information between Cisco devices.

48
00:03:57,000 --> 00:04:02,000
LLDP allows me to see information of non Cisco devices.

49
00:04:02,000 --> 00:04:10,000
In my GNS3 topology, I could run LLDP on these switches.

50
00:04:10,000 --> 00:04:15,000
So on switch 1 as an example, I can type lldp run

51
00:04:15,000 --> 00:04:22,000
no CDP run so I’ve disabled CDP on switch 1

52
00:04:22,000 --> 00:04:25,000
but I’m running LLDP on switch 1.

53
00:04:25,000 --> 00:04:33,000
On switch 2 will enable LLDP and list CDP running.

54
00:04:33,000 --> 00:04:38,000
So on switch 2 sh cdp neighbors

55
00:04:38,000 --> 00:04:43,000
I can see various Cisco devices notice switch 1 timers

56
00:04:43,000 --> 00:04:49,000
are less than a 120 seconds because they're timing out

57
00:04:49,000 --> 00:04:55,000
so the CDP timers are timing out but sh lldp neighbors

58
00:04:55,000 --> 00:05:00,000
shows me switch 1, so I can see switch 1 but I can't see switch 3

59
00:05:00,000 --> 00:05:05,000
and switch 4 because switch 3 and switch 4 are not running LLDP

60
00:05:05,000 --> 00:05:12,000
so as an example on switch 3 show lldp neighbor

61
00:05:12,000 --> 00:05:18,000
we can see that LLDP is not enabled but CDP is enabled

62
00:05:18,000 --> 00:05:23,000
and we can see that switch 1 is going to timeout

63
00:05:23,000 --> 00:05:29,000
where’s something like router 1 has been reset because of the CDP updates.

64
00:05:29,000 --> 00:05:36,000
So you can run CDP at the same time as LLDP

65
00:05:36,000 --> 00:05:39,000
like I’m doing here on switch 2

66
00:05:39,000 --> 00:05:42,000
CDP will show me devices that are running CDP

67
00:05:42,000 --> 00:05:46,000
LLDP will show me devices running LLDP

68
00:05:46,000 --> 00:05:53,000
so in a moment, switch 1 is gonna timeout as its stand here

69
00:05:53,000 --> 00:05:56,000
so we don’t see switch 1 through CDP

70
00:05:56,000 --> 00:05:59,000
but we do see it through LLDP.

71
00:05:59,000 --> 00:06:06,000
Remember LLDP is most useful when you have got none Cisco devices

72
00:06:06,000 --> 00:06:11,000
so like in this example on 3750

73
00:06:11,000 --> 00:06:15,000
I can see Linux based servers that are running LLDP

74
00:06:15,000 --> 00:06:20,000
I'd also be able to see devices such as Cisco IP phones running LLDP

75
00:06:20,000 --> 00:06:26,000
as well as non Cisco routers and switches from vendors such as HPE.

76
00:06:26,000 --> 00:06:31,000
Link Layer Discover Protocol is essentially an industry standard version

77
00:06:31,000 --> 00:06:36,000
of Cisco Discovery Protocol or CDP