L2 vs L3 Trunking

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Jul 17th, 2008
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Could someone explain to me the difference between L2 Trunking vs L3 Trunking?


This is mentioned in a Cisco document "Catalyst 3560 Switch Software Configurtion Guide" under Configuring VLANs Trunks.


I appreciate the help in advance,

sK

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garytayl Thu, 07/17/2008 - 10:30
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In a nutshell, L3 trunking is accomplished by configuring sub interfaces on a particular layer port while L2 trunking is done with a couple of commands in a single interface (with no subinterfaces).


Hope it helps

Edison Ortiz Thu, 07/17/2008 - 10:41
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There is no such thing as Layer3 trunking.


Trunking is the ability to carry more than one vlan via a link. This is a strictly a Layer2 feature.


Perhaps, you are referring to Layer2 vs Layer3 Etherchanneling?


BTW, I read the document you are referring to, I don't see any mentioning of Layer3 trunking anywhere.


HTH,


__


Edison.

garytayl Thu, 07/17/2008 - 10:47
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Edison,


In the documentation I found a note saying:


"The switch does not support Layer 3 trunks; you cannot configure subinterfaces or use the encapsulation keyword on Layer 3 interfaces."


So I guess that is the reason of the question.



Gary

izackvail Thu, 07/17/2008 - 10:56
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I think the document is just saying that the switch doesn't support trunking on a Layer 3 interface.


In other words you can't issue the command no switchport and then try and use that interface to form a trunk.

Edison Ortiz Thu, 07/17/2008 - 10:59
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Gary,


I see the confusion.


I much prefer calling that sub-interface rather than Layer 3 trunk but I see the message the documentation is trying to convey.


Good catch, I missed that little section before.


Thanks


__


Edison.

skhirbash Thu, 07/17/2008 - 11:48
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Correct. The mentionning of L2 vs L3 trunking was on page 12-20 under the note section. Sorry for not making that clear in my original inquiry.


Thanks to all for your responses. I understand it now.


sK

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