layer 3 switching vs layer 3 routing in core

[carl_townshend]

Hi all, people talk about layer 3 switching is best in the core, but what is the alternative, as it layer 3 means routing. does it mean that you should use a multilayer switch where the traffic is switched in hardware rather than cpu?

[rohitrattan]

Hello Carl,

Every thing at layer 3 is essentially routing, routers usually do routing look-up in the memory and with CEF turned on they mimic the switching behavior of a multilayer switch whereas a switch will cache the routing table, entire or a part of it depending upon the resources available, to the hardware table (TCAM) and will work faster. You can have a multilayer switch at the core but routers have a lot of features that are not there in the switch, you may need those at any point in time.

Regards

Rohit

[Joseph W. Doherty]

". . . people talk about layer 3 switching is best in the core, but what is the alternative . . ."

L2 core. (Before multilayer switches, often offered better raw forwarding performance. Even now, still usually offer better performance for the price.)

". . . does it mean that you should use a multilayer switch where the traffic is switched in hardware rather than cpu?"

Doesn't have to, but multilayer switches often used to trade off performance (usually better) vs. features (usually worst) over a router.