Velocity Reviews - Computer Hardware Reviews

Velocity Reviews > Newsgroups > Programming > Java > Re: how to detect MAC address

Thread Tools

Re: how to detect MAC address

Posts: n/a
Sudsy <(E-Mail Removed)> wrote:
> I'm amazed by how many times this topic arises. I can only surmise
> that people are trying to use the MAC address for some licensing
> scheme. I almost hate to tell them that there are ethernet cards
> out there which allow you to reconfigure the MAC address. As long

Well that's a driver / software thingie. Almost any card can do it.
Actually, I've never seen one that couldn't do it.

It is just that the rumor that the MAC addresses are unique and
unchangeable without an eprom burner still floats around.

But that is simply wrong.

The MAC address *is* set statically in a NIC, so much is true. It is
further true that in most cases the MAC address can only be changed by
exchanging the eeprom. However, the MAC address is only read out of the
card once at boot time (or rather, the time when the NICs driver starts and
initializes the card) and then the MAC address is stored in memory in the
OS network driver.

The driver puts together data packets, not the NIC, the NIC has to bring
the data on the wire, but the OS "fills in" the data into the frame. So its
a pure driver thing. All you need is a driver which allows you to override
the default value that is provided by the NICs eeprom.

And most drivers do, since without that feature, you couldn't do failover
and other high-availability functions.

> as you don't have more than one machine on the LAN segment with
> the same MAC then you don't have a problem with routing.

You can always override the value and create a collision by hand. There are
some very specific and rare cases where it makes sense to do so. Generally
its a very bad thing. But it can be done. You shouldn't though, unless you
know exactly what you do.

The bottom line for everyone else is: Trusting on a static never changing
MAC address is no more secure than trusting on a static, never changing IP
address. (there are people around who tell you to configure a firewall to
filter on MAC address instead of IP addresses, since MAC addresses are
static. This is very untrue)



-------------------- http://NewsReader.Com/ --------------------
Usenet Newsgroup Service New Rate! $9.95/Month 50GB
Reply With Quote

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are Off

Similar Threads
Thread Thread Starter Forum Replies Last Post
Differnce between setting mac address port security under theinterface vs. the mac address-table global command ttripp Cisco 5 02-05-2010 10:49 PM
Detect MAC address on (remote) NIC ? Dutch Treat Computer Support 0 03-06-2004 08:34 PM
Re: how to detect MAC address Roedy Green Java 16 07-05-2003 04:32 PM
Re: how to detect MAC address Roedy Green Java 0 07-01-2003 05:29 PM
Re: how to detect MAC address Jon A. Cruz Java 8 06-30-2003 04:50 AM