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I am trying to grasp the idea of how a switch communicates.

Does a layer 2 switch require the entire stack to do it's job, same for layer 3?

If a switch can support SNMP which sits on top of UDP, it must have a full stack?

I believe most switches have some type of network operating system if any at all, so it is hard to understand what a switch actually entails.

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It may be helpful to separate the forwarding functions of the switch from the management functions. We often refer to these as the "forwarding plane" and the management plane."

The management functions can include snmp, telnet, ssh, ftp, tfp, etc. For these to work, the switch needs an OS, and in fact most switch OS are based on some form of *nix.

The forwarding function does not need any of that. In most switches, all the forwarding is done in hardware, so there isn't a "stack" in the software sense.

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  • 'so there isn't a "stack" in the software sense' Even in the hardware sense, I'd say a pure L2 switch has no TCP/IP stack (it does not even need to know about IP)
    – leonbloy
    Jun 10 '16 at 23:37
  • Though I get the impression that modern "L2" switches aren't exactly "pure". Multicast support, protection against rouge DHCP servers etc require the switch to have higher-level knowlage. Jun 11 '16 at 1:43
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A layer-2 switch with management capabilities has the same network stack as a client computer. What it lacks are the routing protocols and other bits found in an L3 device.

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