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ChrisB
2005-11-16, 10:04
Is the MAC address listed on the bottom of the SB3 still the address of
the Ethernet connector, and the wireless MAC is this +1?

Thanks,

Chris

radish
2005-11-16, 14:04
They're both the same.

MrC
2005-11-16, 14:10
Should be the same, but aren't always: See bug:

http://bugs.slimdevices.com/show_bug.cgi?id=2221

ChrisB
2005-11-16, 14:16
Thanks - Google had since told me the same.

It struck me as a little odd, so I'm curious - can someone with a lot
more network knowledge than me explain why this is OK (sharing an
address between two interfaces) and why it was done?

-----Original Message-----
From: discuss-bounces (AT) lists (DOT) slimdevices.com
[mailto:discuss-bounces (AT) lists (DOT) slimdevices.com] On Behalf Of radish
Sent: 16 November 2005 16:05
To: discuss (AT) lists (DOT) slimdevices.com
Subject: [slim] Re: MAC address


They're both the same.


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radish
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MrC
2005-11-16, 14:37
If the SB didn't do that, the wireless interface would be required to "listen" to two MAC (Ethernet) addresses. These devices typically listen to one and only one MAC address, or they can be put in promiscuous mode to listen and receive all.

Packets are sent along the wire (or wirless) using the destination's MAC address. Ethernet devices typically listen to and pickup only packets destined for their own MAC address, and reject others. So, the wireless interface would have to check packets for both MAC address, which is less efficient.

When only one interface is used, there's no issue.

When both are used, packets arrive via wireless, and are forwarded to the Ethernet port. There can be many devices behind the bridge. The SB can maintain a simple MAC/IP connection table - forwarding through the bridge all that isn't destined for itself.

ChrisB
2005-11-16, 15:22
So essentially it was done to make bridging work without putting
additional strain on the wireless card?

-----Original Message-----
From: discuss-bounces (AT) lists (DOT) slimdevices.com
[mailto:discuss-bounces (AT) lists (DOT) slimdevices.com] On Behalf Of MrC
Sent: 16 November 2005 16:37
To: discuss (AT) lists (DOT) slimdevices.com
Subject: [slim] Re: MAC address


If the SB didn't do that, the wireless interface would be required to
"listen" to two MAC (Ethernet) addresses. These devices typically
listen to one and only one MAC address, or they can be put in
promiscuous mode to listen and receive all.

Packets are sent along the wire (or wirless) using the destination's
MAC address. Ethernet devices typically listen to and pickup only
packets destined for their own MAC address, and reject others. So, the
wireless interface would have to check packets for both MAC address,
which is less efficient.

When only one interface is used, there's no issue.

When both are used, packets arrive via wireless, and are forwarded to
the Ethernet port. There can be many devices behind the bridge. The
SB can maintain a simple MAC/IP connection table - forwarding through
the bridge all that isn't destined for itself.


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MrC
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MrC
2005-11-16, 18:10
So essentially it was done to make bridging work without putting
additional strain on the wireless card?
No, thats not it. 2 MAC addresses are simply not necessary.

Here's a simplification. Think of the SB acting like a switch wrt. forwarding packets between the networks. A switch has no need for MAC addresses for each of its ports. And think of the SB device itself (ie. an ethernet device that plays music) as the part that requires a MAC address.

The bridge will learn about devices that reside on each side of the bridge. LAN A can only transmit packets to the port A side of the bridge and LAB B can only transmit to the B side. There's no confusion or problems. The bridge broadcasts and forwards as necessary based upon the MAC addresses it has learned when a station transmits a packet.

ChrisB
2005-11-17, 07:11
Thanks for the explanation!

-----Original Message-----
From: discuss-bounces (AT) lists (DOT) slimdevices.com
[mailto:discuss-bounces (AT) lists (DOT) slimdevices.com] On Behalf Of MrC
Sent: 16 November 2005 20:10
To: discuss (AT) lists (DOT) slimdevices.com
Subject: [slim] Re: MAC address


ChrisB Wrote:
> So essentially it was done to make bridging work without putting
> additional strain on the wireless card?
No, thats not it. 2 MAC addresses are simply not necessary.

Here's a simplification. Think of the SB acting like a switch wrt.
forwarding packets between the networks. A switch has no need for MAC
addresses for each of its ports. And think of the SB device itself
(ie. an ethernet device that plays music) as the part that requires a
MAC address.

The bridge will learn about devices that reside on each side of the
bridge. LAN A can only transmit packets to the port A side of the
bridge and LAB B can only transmit to the B side. There's no confusion
or problems. The bridge broadcasts and forwards as necessary based upon
the MAC addresses it has learned when a station transmits a packet.


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MrC
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