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New Member

L2 switch operations - security ACL

hi experts,

I would like to ask you something aobut L2 switch...

I don't know how  is possible that L2 switch may to performe some  checking (security  ACLs) on layer3 and layer4? How is this possible omg, that's L2  switch...

from switch book:

security ACLs—Access control lists (ACL) can be used to identify frames  according to their MAC addresses, protocol types (for non-IP frames), IP  addresses, protocols, and Layer 4 port numbers. The ternary  content-addressable memory (TCAM) contains ACLs in a compiled form so  that a decision can be made on whether to for-ward a frame in a single  table lookup.

Can someone explain me how it's possible.

IMPORTANT:I am not talking about MLS I am talking about pure L2 switch.

THANKS for replies.



L2 switch operations - security ACL

  Although considered l2 switches ,  they can obviously look deeper into the packet and  have acl functions .  L2 switches like the 2950,2960 series  can indeed do acl's though only on the inbound direction at least on the older 2950 series and there are other restrictions in doing acl's on a l2 switch .  I think eventually cisco will probably do away with a so called l2 switch and make  everything be able to route if even at a basic level .  They have already done this on the latest codes for the 2960 series.

Cisco Employee

L2 switch operations - security ACL

Glen is right.

Traditional l2 switches don't exist anymore. Even before the new code that allows basic L3 routing with 16 static routes, the 2950/2950 was already MLS at least for as far as QoS and Security ACL are concerned. In fact you would use the mls commands for lots of features. So also a L2 switch as the 2960 is able to inspect the traffic at layers 3 and 4 too.


New Member

Re: L2 switch operations - security ACL

thx glen for fast reply...

but I don't understand why cisco teach (us) something different (in their books ) from that what's in real...


riccardo: thx too.  I must accpet that L2 switch (as I know them from theory) doesn't exist anymore. THX for explanation.

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