01-21-2012 04:53 AM - edited 03-07-2019 04:28 AM
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.
pepso
01-21-2012 05:08 AM
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.
01-21-2012 05:16 AM
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.
Riccardo
01-21-2012 05:20 AM
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...
edit:
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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