MAC addresses in router vs Access Point

MAC addresses in router vs Access Point
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Subject Author Date
MAC addresses in router vs Access Point Ale 05-01-2008
Posted by Albert Manfredi on May 1, 2008, 3:37 pm
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> Does a switch without spanning-tree need any MAC address? =A0If so,
> does it need more than one?

By "switch," I did mean bridge. Sorry for not being more specific.

I suppose that a managed switch, implementing no spanning tree
protocol, would need at least one MAC address, so that it can be
reached by an IP host. Other than that, should be similar to a hub
(repeater), in terms of addressing needs.

> But without a router function, why two addresses?

Hmm. Good point. If the access point has no router function, one could
consider it to be a mere repeater. My reason for saying that it needs
two MAC addresses was only because this is the only way to allow
unambiguous addressing of the wired and wireless interfaces, even if
in the same IP subnet. I suppose you could argue that addressing the
two interfaces is not mandatory at all. So I stand corrected.

Bert

Posted by ps56k on May 3, 2008, 1:38 pm
Ale wrote:
> why does an access point have 2 MAC addresses (one WLAN, one LAN)
> while a router has only one even if it has lan ports and wan ports?
>
> thanks!

an Ethernet device has a MAC to facilitate media communications.
No MAC - no communications.... hence the acronym.
This MAC may be merely copied from other incoming data frames,
as with a hub, switch, or bridge.

However, if the device is "smart" and needs to be addresses via IP or some
other higher protocol,
the device really needs a MAC of it's own, so any address resolution (ARP)
can find it on the network.

If a general home router has a a LAN and WAN interface - both Ethernet -
then it will probably have 2 MACs, one for accessing the router from each
"world".

Other high end routers (or switches) have a MAC,
and a corresponding IP address to access and manage the entire device.




Posted by ps56k on May 3, 2008, 2:21 pm
ps56k wrote:
> Ale wrote:
>> why does an access point have 2 MAC addresses (one WLAN, one LAN)
>> while a router has only one even if it has lan ports and wan ports?
>>
>> thanks!
>
> an Ethernet device has a MAC to facilitate media communications.
> No MAC - no communications.... hence the acronym.
> This MAC may be merely copied from other incoming data frames,
> as with a hub, switch, or bridge.
>
> However, if the device is "smart" and needs to be addresses via IP or
> some other higher protocol,
> the device really needs a MAC of it's own, so any address resolution
> (ARP) can find it on the network.
>
> If a general home router has a a LAN and WAN interface - both
> Ethernet - then it will probably have 2 MACs, one for accessing the
> router from each "world".
>
> Other high end routers (or switches) have a MAC,
> and a corresponding IP address to access and manage the entire device.

just a note to the OP -
what device are you talking about ?
ie -
on my Linksys WAP 54G WiFi access point (not a router),
the same MAC is used for the LAN and the WiFi (WLAN).

but on my Linksys router (no WiFi)
it has a different MAC for the LAN (4 port switch)
and for the WAN (connected to DSL modem)

Don't confuse WLAN (Wifi) vs WAN (wide area network = cable or DSL)




Posted by ps56k on May 3, 2008, 5:43 pm
Ale wrote:
> why does an access point have 2 MAC addresses (one WLAN, one LAN)
> while a router has only one even if it has lan ports and wan ports?
>
> thanks!

BTW - here's some general reading -
for a general type MAC question
http://en.wikipedia.org/wiki/MAC_address

without getting down in all the nuts and bolts of 802.xx




Posted by Ale on May 6, 2008, 3:05 am
wow, thanks for all the responses, but it's getting confusing now.

My soho wireless router has a label for a WLAN MAC and a LAN MAC. The
LAN MAC is used on the WAN port (it gets an IP address assigned by
the upstream router on its network).
Why don't the 4 switch ports also need a MAC address? Or do they get
the MAC of the device that's plugged into it?
When I configure the router by the IP address on the LAN side, doesn't
this need a MAC too?



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