Linked by Howard Fosdick on Mon 21st Nov 2011 07:48 UTC
Google Last June, CNET disclosed that Google collects and publishes the estimated locations of millions of phones, laptops, and other Wi-Fi devices. All without their owner's knowledge or permission. Google has finally announced how to exclude your home network from this database. Simply append "_nomap" to its name. Details over at CNET. Left unsaid is why the burden is placed on millions of individuals to opt-out, instead of on perpetrator Google.
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RE[4]: Comment by clhodapp
by phoenix on Tue 22nd Nov 2011 18:41 UTC in reply to "RE[3]: Comment by clhodapp"
phoenix
Member since:
2005-07-11

Soulbender,

"In practice MAC addresses are not unique (and don't actually have to be)."

I really would like to know what you mean here, because in practice having duplicate MAC addresses will break things like DHCP and switching hubs which rely on a MAC address's uniqueness.


MAC addresses have to be unique only within the same broadcast domain (ie, subnet). MAC addresses do not have to be unique on separate subnets, even if within the same building.

Most consumer wireless routers will automatically clone the MAC address of the computer it's connected to, using that MAC address on it's WAN interface. You then have two devices in the same location with the same MAC address. But, they are on separate subnets, in separate broadcast domains, so it all works.

Reply Parent Score: 2

RE[5]: Comment by clhodapp
by Alfman on Tue 22nd Nov 2011 21:37 in reply to "RE[4]: Comment by clhodapp"
Alfman Member since:
2011-01-28

phoenix,

"MAC addresses have to be unique only within the same broadcast domain (ie, subnet). MAC addresses do not have to be unique on separate subnets, even if within the same building."

Thank you for the response, I already know how they work though. The hardware MAC is designed to be unique globally, even if it's only necessary to be unique locally. It is not a misunderstanding on my part.

To my knowledge we still haven't needed to recycle them in hardware. If you know of a source that talks about manufacturers reusing MACs, I'd love a link.

http://anonsvn.wireshark.org/wireshark/trunk/manuf

There appear to be plenty of unassigned entries left scattered throughout.

Edited 2011-11-22 21:40 UTC

Reply Parent Score: 2