At 04:46 PM 2/25/2003 +0000, Robert Edmonds wrote:
>Layer 3 switching combines the best of switching and routing in one
>platform. The main advantage here is speed. The way it works is, in a
>switch you have some kind of layer 3 routing engine (aka route processor, or
>RP). For example, the MSFC2 (Multilayer Switch Feature Card 2) is one of
>the options available for the Cisco 6500 (and a couple of others, I think)
>switches. When the switch receives a packet bound for a different VLAN, it
>sends it to the RP. The RP makes the routing decision and puts an entry in
>the route cache for the switch. The first packet in a flow is routed and
>the rest are switched at wire speed, hence the increase in speed. That's
>kind of a simplified view, but I think it gets the general idea across. So,
>layer 3 switching is both routing and switching, but faster (usually,
>anyway).
One should keep in mind that many vendors including Cisco have been capable
of doing per packet routing at wire speed for some time and thus this
"advantage" is a legacy attribute.
>""DeVoe, Charles (PKI)"" wrote in message
>news:200302251554.PAA06930@xxxxxxxxxxxxxxxxx
> > I am under the impression that switching is a layer 2 function and that
> > routing is a layer 3 function. I have seen several discussions talking
> > about layer 3 switching. Could someone explain this to me?
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