From: Brian McGahan (brian@mcgahan.com)
Date: Tue Jul 22 2003 - 22:52:36 GMT-3
Pierre,
The new generation of layer 3 switches forward frames up to
layer 4 as fast as they do at layer 2. Therefore, Cisco's new switch
block design model recommends layer 3 down to the access layer. Since
L3 is now down to the access layer, your L3 routing protocols are
sitting on top of your L2 spanning-tree domain.
If there is an outage in the network, spanning-tree must
reconverge before your layer 3 routing protocol can reconverge.
Therefore, the simplest solution is to run all inter switch links as
native layer 3 interfaces, removing the added convergence time of
spanning tree protocol.
Apply this principle to an EtherChannel, and now it's possible
to have an aggregate link of up to 4Gbps interconnecting switches
without running spanning-tree.
HTH,
Brian McGahan, CCIE #8593
brian@mcgahan.com
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> pierreg
> Sent: Tuesday, July 22, 2003 3:08 PM
> To: ccielab@groupstudy.com
> Cc: byme88@yahoo.com
> Subject: Layer 2 Etherchannel versus Layer 3 Etherchannel
>
> What I understand:
>
> With a Layer 2 Etherchannel you group layer 2 interfaces together.
With a
> Layer 3 Etherchannel you combine multiple Layer 2 interfaces as one,
then
> you assigned them an IP.
>
> What I want to know?
>
> I assume if they created this new technology it's because it must have
> been needed. Can some one give me a (real life) example of the kind of
> problems Layer 3 Etherchannel solve? If you don't have a real life
> example, a hypothetical one is OK too.
>
> Thanks,
>
> Pierre-Alex
>
>
>
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