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This question is mainly about the logic of unmanaged switches.

I've seen posts here and elsewhere saying that it's okay to plug in a switch to a SOHO router (using a crossover if necessary), which is basically the same as plugging a switch into a switch. I need to do this for a business to extend the amount of ethernet ports on their router.

I don't understand how this is possible. Won't the router see many computers connected to one port, thus resetting what mac address it thinks is at that port every time a new message is sent? I would think that would have performance consequences, unless I'm wrong here.

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up vote 7 down vote accepted

Any non-braindead switch implementation understands multiple MAC addresses per port. What you're proposing doing is fine, and perfectly normal.

(Your SOHO router is actually a router and a switch combined into one device)

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And the router part of the device only cares about Layer 3: source and destination address, the switch takes care of what port has what MAC, etc. –  gravyface Jul 29 '10 at 21:03
    
Thanks derobert and gravyface. That's exactly the answer I needed. –  Caleb Hearon Jul 29 '10 at 21:15
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Of course there is a limit to the number of physical address. A cheap switch may have a relatively small cam table so if you added a couple thousand computers your switch might start acting like a hub. –  Zoredache Jul 29 '10 at 22:11
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