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Why does my router have three MAC addresses?


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#1
caljohn

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I have the ubiquitous Linksys WRT54G router, and when I go into its configuration settings under "Status", I can choose either "Router", "Local Network", or "Wireless." All of those sections list a MAC address that is slightly different--only the last hex digit varies:

Router: 00:14:BF:D6:CD:29
Local Network: 00:14:BF:D6:CD:28
Wireless: 00:14:BF:D6:CD:2A


So since my router is hooked up to my DSL modem, my DSL modem sees the "Router" MAC address, but any computer that uses the router on the LAN will see either the LAN or wireless MAC address, depending on whether they are connected via ethernet or wireless.

So the question is, why are there three MAC addresses for the same router? I thought the whole point of the MAC address was to uniquely identify the router, and I don't see how there would be any networking conflicts if one MAC address was used in all the above three cases. So why not just use one MAC address?

Thanks for any insight/help. :)

Edited by caljohn, 15 July 2008 - 07:25 PM.

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#2
The Admiral

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I thought the whole point of the MAC address was to uniquely identify the router.

You're almost right: the MAC address is meant to uniquely identify each device in the network. Your router has 3 MAC addresses for the same reason your laptop can have 3 MAC addresses - a bluetooth, wired NIC, Cellular (WWAN), and WiFi cards could technically be used on the same network at once, or, on different networks. What if your computer is trying to send data from 00:14:BF:C3:16:0B, but that MAC address is assigned to both the bluetooth and the WiFi card? What if your computer is connected to your router using both a wire and wireless - what if you just need to send data through the wired link and not the wireless?
So it's not all about physical devices, but actual nodes on a network. :)
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#3
dsenette

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good answer!
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#4
The Admiral

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I lerned something in Netwerk+!
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#5
dsenette

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stranger things have happened hehehe
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#6
caljohn

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Thanks, "The Admiral", that makes a lot more sense now. Of course for most typical home applications it would never be an issue, but the special cases you describe I see where it could lead to problems having only one MAC address for all interfaces. I like to know the details and reasons behind these things, so thanks for explaining. :)
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#7
The Admiral

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Just make a new post if you need to know anymore intricasies, like ARP, NAT, DNS, or NORAD. :) Glad I could clarify for you.
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