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Changing MAC Address/ifconfig? Network
Anyone know how to change the MAC Address on the ethernet card?
I've been trying ifconfig but I can't seem to get it to work.

My cable provider registers MAC address and I switch back and forth between two machines. I don't want to use a router. Any help would be appreciated.
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out of luck..
Authored by: aaronfaby on May 17, '01 03:21:39PM

As far as I know.. MAC addresses can't be changed. They are hard coded into the NIC
cards, kinda like fingerprints, no two NICs can have the same MAC address. Sorry.


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out of luck..
Authored by: jgmanning on May 17, '01 03:42:31PM
Actually, some guys came up with a way to do this, but it only runs on OS 8 - 9.0.4:

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What MAC addresses are for
Authored by: _merlin on May 17, '01 06:33:58PM

The whole idea of a MAC address is so that each and every network card in the world can be positively identified. The ability to change your MAC address would defeat this purpose, and create a possibility for hardware address conflicts, which would be almost impossible to find and correct on large networks. The MAC address is hard-coded into most network cards.

Vasantha Crabb

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Authored by: Cadre on May 17, '01 09:00:57PM

The purpose of a Mac address isn't so that all ethernet cards can be positively identified. Mac addresses are different so that communication over the IP layer is possible. Mac addresses can be the same (though, unless you are manually changing them, this will never happen) they just can't be the same on the same LAN.

It used to be that one could change the mac address just by typing "ifconfig en0 lladdr new_mac_address" with some cards. On others you couldn't, you would have to patch a couple system calls (do a search on google for setmac.c and/or module_3.0) and that would also work. I haven't run across a way to do with with MacOS X and the gigabit cards though.

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Authored by: _merlin on May 18, '01 01:55:37AM

You seem to have misunderstood what I meant. I meant that a MAC address is supposed to be unique, so that even if you created a LAN containing every network card in the universe, they would all have a different MAC address, and therefore be individually distinguishable. If two had the same MAC address, the messages destined for either of them would be received by both, and messages from either of them would appear to be coming from a single card. This is why each and every network card manufactured has a MAC address hard-coded into it.

The ability of software to change MAC addresses does not change these hard-coded addresses. It merely makes a temporary change to the address the card is using. If you reset the card, it will return to its hard-coded address.

In summary, I do realise that it is possible to change the address that a card uses, it is not possible to change its hard-coded address. The way cable modems latch onto a single MAC address is not a particularly good security measure. It doesn't take into consideration the fact that a user may upgrade their network card or computer, and doesn't allow a user to share one modem between two or more computers. Changing our MAC addresses to circumvent this shortcoming doesn't solve the problem. It is merely hiding from it. Let's tell the cable modem manufacturers what we think of this scheme, and pressure them to change.

Vasantha Crabb

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reset cable modem
Authored by: mug1 on May 18, '01 05:26:35AM

to use more than one comp with ur cable-modem
u need to disconnect/reconnect to power.
or reset if u have a botton.

or use a router

or use a two networkcard setup on the first comp

i dont think theres another way.... i hate it.

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One option is an Airport basestation
Authored by: sjonke on May 18, '01 12:53:36PM

You can use an Airport Base Station to share a cable-modem, not to mention wireless networking of your computers. Not the cheapest option, certainly, but If you happen to have a portable or plan to get one (how 'bout that new iBook?) you will be loving life if you get a base station. I recently got an (older) iBook and tried out an airport base station and card with it at home (for me, just over a dial-up connection.) It is, to say the least, extremely nice. It would be even better with a cable-modem. It was painful to have to take the base station back to work. :( Eventually I'll get my own for home. Yes, it works great with OS X, however, to set it up you will want to boot into OS 9. There are some 3rd party tools to do it on X, but Apple's OS 9 tools are much easier to use.

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Contact your provider
Authored by: milney on May 18, '01 01:11:27PM

I don't know about your cable provider, but I can contact mine and give them a number of MAC addresses should I wish to use more than one computer!

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One option is an Airport basestation
Authored by: paulio on May 23, '01 06:34:45PM

I can confirm that an Airport base station will route with AT&T @home cable as well as with PacBell DSL.

The interesting thing is that the Airport has only one Ethernet port. I once thought that this kind or routing needed two ethernet ports, one for the internal network and one for the external cable/DSL modem. Apparently, only one ethernet port is required.

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Not if your ISP doesn't allow routers
Authored by: raf on May 24, '01 01:05:24AM

One of the reasons MAC addresses exist is to allow network verification. Some ISPs don't want you sharing your high speed access with everyone else in your dorm (what a shocker) or entire apartmet building, so they won't allow routers on their network. The Airport base station is a router. If you have such an ISP, then an Airport base station wont help you. Your ISP simply won't let the Airport base station on the network, since it's not the MAC of one of the network cards they've approved (when you sign up, or add a new computer by calling their tech support).

What you want is a *software* base station. Use one mac equipped with an airport card as a software base station. This machine will be the always-on router. The other machines with airport will be effectively invisible to your ISP (all their requests will look like they're coming from the software base station machine).

If you want to use cabling instead of airport, then you need second ethernet card in your router mac, and a product like IP NetRouter to do the routing.

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you could use gNAT
Authored by: alexkent on May 29, '01 03:13:18PM

you can use gNAT to setup software network address translation within osX which would alow you to share the connection between the two machines. i think gNAT is available form the apple osx software download area. if not, try

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mac address
Authored by: debruyng on Jul 14, '01 09:34:36AM

You can solve this problem with Asante's friendlynet cable router.
It can show any mac adress to your provider.

Take a look to the specs at:


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Change the MAC address
Authored by: Embro on Jan 16, '02 11:32:30AM

I have been looking for this answer for quite some time and have finally found it. It is complicated but can be done.

Let me know if anyone tries this.

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Change the MAC address
Authored by: me0 on Mar 20, '02 06:43:48PM

I found that place as well and as far as the instructions given everything went well (recompiled xnu and everything). Only I still don't know howto change the mac address since I can't get nemesis to compile (actually can't install netlib) and ettercap is a strange beast which doesn't seem to want to change anything for my system. I read something on (development section) about an enchanced version of ifconfig. The current one really sucks I tell you. Bah, damn BSDs...

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