Post by Steve Pope Post by Jeff Liebermann Post by Steve Pope
I think we're in agreement that the wireless router should have
three assigned (i.e. hardware) MAC addresses. I do not think a
dual-band radio needs to have two actually.
Dual band radio requires a MAC address for each band or bridging
between the two radios would not work.
I agree. But, most dual-band WiFi implementations do not
contain two radios, they contain only one dual- (or multi-) band
radio, along with one baseband processor, and one lower MAC; and have
a single BIA MAC address (using Roy's terminology).
There may be situations where such a single-radio dual-band WiFi
device could be made to made to look like it is bridging between two bands
(or for that matter, between two different channels in the same band).
Well, yes if it's a client. In the current way of doing things, you
can only connect to a single access point with a client radio. Yes, I
know there are new and wonderful protocols and hacks that allow more
than one connection, but I'm talking about the typical client radio,
such as a laptop, tablet, or smartphone. So, for one of these client
radios, you only need one MAC address because one never has both bands
connected to something at the same time. Dual band wireless sniffing
doesn't count because the client radio never associates with any of
the AP's (or clients) that it's sniffing.
Well, let's see if that's true. My Google Nexus 7 (2013) does dual
band and uses a Qualcomm/Atheros WCN3660 chip:
For a nominal $5,000, I get to find out what's inside without an NDA:
The press release doesn't help much:
Ah... it has a LTE/ISM coexistence which implies that only one radio
is on at a time. Ok, it's one radio with BT/LTE/WiFi on only one at a
I'm having a hell of a time finding an app that will deliver my
tablet's MAC address. So far:
Settings -> WiFi -> Advanced
shows the same MAC address for whether I connect to my router on 2.4
or 5GHz. So, for the client, it's probably a single MAC address for
However, looking at all the dual band wireless routers on the shelf,
all of them have a different MAC address for each radio and most seem
to have different chips for 2.4 and 5GHz. For example, I've been
pushing Linksys EA2700 routers (because I got a bunch of them cheap).
It uses a Broadcom BCM47186 for 2.4Ghz and a BCM43236 for 5GHz. See
photo and notice that the 2x antennas each go to a separate shielded
section on the PCB.
If I do find a wireless router with only one Wi-Fi chip, I would also
expect to find that it won't do 2.4/5 Ghz simultaneously and if it did
happen to support 2.4 <-> 5Ghz bridging, it would be dreadfully slow
due to multiplexing.
Post by Steve Pope Post by Jeff Liebermann
I worked with a prototype
AP that had a 900 MHz, 2.4GHz, and 5GHz radios in one box, each radio
with a different MAC address.
Sounds pricey ... but one assumes, targeted for bridging applications.
Yep. It died after the first prototype. This was long before
802.11ah. Ubiquiti was selling their flavor of 900 Mhz 802.11 style
chips, which was suppose to be an option. It had 4 mini-PCI slots
that could handle various combinations of radios. My job was keeping
the radios from desensitizing and interfering with each other. I'm
rather glad it died because I the coupling was so horrible, that I
don't think I could have made it work without expensive shielding.
Post by Steve Pope
I can almost guarantee you that when 802.11ah (900 MHz WiFi) devices
become widely available, none of them will have a separate 900 MHz
radio, they will all be dual- or most likely tri-band radios.
I would agree for the client side (tablets, smartphones, and laptops).
I'll disagree for the wireless router side, which methinks needs
separate radios or the performance will be disgusting and bridging
between wireless ports will be slow or impossible.
Post by Steve Pope
What you might at that point see is AP's that contain three
tri-band WiFi chips, each configured to operate in only one band.
(Just a prediction, based on what I'm seeing being designed.)
I think Xirrus does exactly that. You plug in a "radio" module, and
program it to do whatever you want. I'm not sure if the antenna needs
to be swapped.
Drivel: Typical Friday. UPS and Fedex arrive with the parts I've
been waiting for all week just before I try to leave. So, I get to
work all night. Argh.
Jeff Liebermann ***@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558