1
00:00:00,000 --> 00:00:08,000
Now on switch 1, sh spanning-tree vlan 1

2
00:00:08,000 --> 00:00:13,000
shows me that gigabit 0/1, 2 and 3 are blocking

3
00:00:13,000 --> 00:00:16,000
so spanning tree are blocking those ports

4
00:00:16,000 --> 00:00:21,000
but when I use the command show cdp neighbors

5
00:00:21,000 --> 00:00:25,000
I do see my neighboring switches even though those ports are blocked.

6
00:00:25,000 --> 00:00:32,000
So management traffic such as CDP, VTP, DTP, LLDP

7
00:00:32,000 --> 00:00:38,000
and others are not blocked through Spanning Tree.

8
00:00:38,000 --> 00:00:42,000
In this example, show lldp neighbor shows me

9
00:00:42,000 --> 00:00:44,000
that I have a neighboring switch

10
00:00:44,000 --> 00:00:50,000
switch 2 connected to gigabit 0/0 as well as to gigabit 0/1.

11
00:00:50,000 --> 00:00:54,000
Gigabit 0/1 is blocking in Spanning Tree

12
00:00:54,000 --> 00:00:58,000
but I'm still receiving those LLDP messages on that blocking port.

13
00:00:58,000 --> 00:01:01,000
Now I don’t see switch 3 and switch 4 in LLDP

14
00:01:01,000 --> 00:01:06,000
because these 2 switches are not running LLDP

15
00:01:06,000 --> 00:01:10,000
but if I went to switch 3 as an example

16
00:01:10,000 --> 00:01:13,000
and enabled Link Layer Discovery Protocol

17
00:01:13,000 --> 00:01:22,000
I should see that switch become available as a neighbor and there you go.

18
00:01:22,000 --> 00:01:26,000
Switch 3 is available as neighbor on gigabit 0/2

19
00:01:26,000 --> 00:01:32,000
even though Spanning Tree is blocking on that port.

20
00:01:32,000 --> 00:01:35,000
By the same token going to switch 4

21
00:01:35,000 --> 00:01:44,000
enable lldp go on to switch 1 show lldp neighbor

22
00:01:44,000 --> 00:01:47,000
I can see switch 4 as an LLDP neighbor

23
00:01:47,000 --> 00:01:50,000
I can also see that switch as a CDP neighbor.

24
00:01:50,000 --> 00:01:53,000
CDP is enabled by default

25
00:01:53,000 --> 00:01:59,000
LLDP is not but both those protocol are received on a Spanning Tree

26
00:01:59,000 --> 00:02:04,000
blocking port so even though this port once again are blocking.

27
00:02:04,000 --> 00:02:09,000
LLDP and CDP are received on that port as well as transmitted.

28
00:02:09,000 --> 00:02:11,000
So back on switch 2

29
00:02:11,000 --> 00:02:15,000
sh cdp neighbor

30
00:02:15,000 --> 00:02:24,000
I can still see switch 1 as a CDP neighbor and as an LLDP neighbor

31
00:02:24,000 --> 00:02:28,000
even though this port is blocking in Spanning Tree

32
00:02:28,000 --> 00:02:33,000
so management traffic such as LLDP and CDP is transmitted

33
00:02:33,000 --> 00:02:38,000
and received on blocking ports or to use industry standard term

34
00:02:38,000 --> 00:02:43,000
on ports that are discarding.