>"Rodney Jackson" <[EMAIL PROTECTED]> wrote,
>Guys,
>
>I need some help. Can someone please explain why Layer 3 Switching
>is faster than Layer 2 Switching? It seems to me that with L3 the
>switch would have to go up three layer instead of two. I may have
>whole concept so please explain.
*sigh* the reason you are confused is that layer 3 switching is
principally a marketing rather than a technical term.
Relaying packets based on layer 3 information is routing.
Relaying frames based on layer 2 information is bridging or
frame/cell switching.
Each of these levels has two components:
Path determination
May contain dynamic routing protocols
Will contain configuration information
Stores best paths in a Routing Information Base(RIB) that is
optimized for efficient updating
May create a Forwarding Information Base (FIB) that is optimized for
speed of lookup. Alternatively, the RIB and FIB may be the same.
Forwarding
Makes forwarding decisions based on the contents of the FIB
When hardware assisted and making layer 3 decisions, often is called
layer 3 switching
So a layer 3 switch is really a hardware-accelerated router.
A layer 2 switch is faster than a traditional bridge, under most
circumstances, because:
It has a very fast internal forwarding fabric interconnecting its ports
It uses microsegmentation on its user ports
It usually will have a hardware-assisted FIB containing layer 2 information
Things are getting more, not less, complex. Multiprotocol label
switching (MPLS) or Cisco's tag switching makes forwarding decisions
based on a label or tag, usually between the layer 2 and 3 headers.
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