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im trying to find the reason why cisco switches have a base mac-address and one for each port?? Can anyone help me to understand this..

  • Mainly so they can be used as non-switchports. Since a switch is fundamentally a transparent layer-2 bridge, nodes don't speak to a port directly. – Ricky Jan 28 '15 at 19:41
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The MAC address is the "hardware address" which uniquely identifies a virtual device (such as an SVI or loopback interface), a host, a port or what-have-you at Layer 2 of your network.

These extra MAC addresses are utilized by managed devices (such as Cisco switches) to provide additional functionality beyond that of a "dumb" switch or hub.

Understanding the 7-Layer OSI Networking Model is critical to your understanding and troubleshooting of networking issues.

http://en.wikipedia.org/wiki/OSI_model

  • A switch (or hub or "bridge") doesn't require a MAC to function -- devices aren't "talking to the port". Look at a simple, unmanaged netgear/linksys switch, notice it doesn't have a MAC at all. – Ricky Jan 28 '15 at 19:43
  • I'll reword my statement, but you know precisely what I mean from the utilization and usage of those MACs on managed devices. – Panther Modern Jan 28 '15 at 19:49
  • at a hardware level i do think switch use mac-addresses to map its own ports.. port numbers are for humans.. and this is why i asked the question to be sure of that... – Gngogh Jan 28 '15 at 20:13
  • learning the osi model as someone refer here does not tell me why switches have a mac-address for each port... yeah, i know how switches identify hosts on a L2 domain.. – Gngogh Jan 28 '15 at 20:28
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As far as I know a switch uses its own MAC address when it needs to send traffic on the control plane. It does not use them when it's performing switching.

  • That is correct. Switching doesn't need a mac. Various services need a MAC. (spanning-tree, layer-3 (ip) interfaces, etc.) – Ricky Jan 28 '15 at 22:57

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