L2 vs L3 Trunking

Unanswered Question
Jul 17th, 2008

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

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

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

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

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

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

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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