How ACL Works on Layer2 Switch

[cool.cisco]

Hi,

Its a basic think but pls help me out..

As per the theorey...layer 2 switch performs the three fuctions mainly, learning forwarding and loop avoidance.

In a multilayer switch we can put the ACL and implement the QOS features.

I am surprised, that we can implement the ACL and QOS features in Layer2 Switch also.

Whereas layer2 switch doesn't understand the Layer3 and above information............

What is this dilema....??????

Does someone knows the answer...

Thx,

[dgahm]

All Cisco switches are store and forward, meaning they receive a full frame before making a forwarding decision. This allows the switch to throw away errored frames, and to look at any field to perform filtering, QOS or whatever is needed.

So the answer is that the current generation layer 2 switch does understand layers 1-4, but forwarding decisions are based on layer 2.

[cool.cisco]

Hi,

Thanks for the answer i completely got it now...

Except you said they understand layer 1-4, i want to add here not only understand but they perform not l3 but l4 functions, like we can implement the Access-lists.........

But another dilema,...if these switches understands l2 and l4 information........how these are being designed that l2 and l4 only....

Respond pls....