WEBVTT

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Now on switch 1, sh spanning-tree vlan 1

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shows me that gigabit 0/1, 2 and 3 are blocking

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so spanning tree are blocking those ports

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but when I use the command show cdp neighbors

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I do see my neighboring switches even though those ports are blocked.

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So management traffic such as CDP, VTP, DTP, LLDP

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and others are not blocked through Spanning Tree.

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In this example, show lldp neighbor shows me

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that I have a neighboring switch

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switch 2 connected to gigabit 0/0 as well as to gigabit 0/1.

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Gigabit 0/1 is blocking in Spanning Tree

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but I'm still receiving those LLDP messages on that blocking port.

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Now I don’t see switch 3 and switch 4 in LLDP

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because these 2 switches are not running LLDP

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but if I went to switch 3 as an example

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and enabled Link Layer Discovery Protocol

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I should see that switch become available as a neighbor and there you go.

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Switch 3 is available as neighbor on gigabit 0/2

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even though Spanning Tree is blocking on that port.

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By the same token going to switch 4

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enable lldp go on to switch 1 show lldp neighbor

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I can see switch 4 as an LLDP neighbor

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I can also see that switch as a CDP neighbor.

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CDP is enabled by default

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LLDP is not but both those protocol are received on a Spanning Tree

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blocking port so even though this port once again are blocking.

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LLDP and CDP are received on that port as well as transmitted.

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So back on switch 2

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sh cdp neighbor

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I can still see switch 1 as a CDP neighbor and as an LLDP neighbor

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even though this port is blocking in Spanning Tree

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so management traffic such as LLDP and CDP is transmitted

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and received on blocking ports or to use industry standard term

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on ports that are discarding.