MAC Address Question

[Vegito]

I know that within 1 network, having 2 NIC with same mac address will confuse the network..

but if I have 3 seperate network and in each subnet, there is one pc with same MAC address that is the same as the other 2 pc in the other subnet, would I run into problem there ?

 

[Boscoh]

Assuming there is a router between each of the subnets, then probably not.

The ethernet address is going get rewritten and become the routers ethernet address anyways. So the receiving station will never know the MAC of the sending station, it will just see the last routing device that forwarded the packet to it.

 

[spidey07]

shouldn't be a problem, mac addresses are only locally significant at layer2.

BUT!!! I wouldn't risk it anyway. duplicate mac address problems are incredibly hard to troubleshoot (mainly because you just assume they are unique), but i've seen where people hard coded them all and the mess it can create.

 

[skyking]

Yes, that sounds like "bad berries" to me also.
On another note: spidey, which network adapters support changine the MAC addy, besides the usual intel ones?

 

[spidey07]

Originally posted by: skyking
Yes, that sounds like "bad berries" to me also.
On another note: spidey, which network adapters support changine the MAC addy, besides the usual intel ones?

I think just about all of them.

 

[Nothinman]

On another note: spidey, which network adapters support changine the MAC addy, besides the usual intel ones?

It's probably dependent on the driver, but AFAIK every driver on unix supports specifying a MAC via ifconfig and I believe you can change just about all of them in Windows via the driver properities too.

 

[Boscoh]

Changing the MAC in windows is as simple as changing a reg key, but it should be in the driver properties too. There are also programs out there that will do this.

 

[thirdlegstump]

You can't run MacOS on Windows. Only Macs can run both OS without issues. To find the Macs address, just go into tcp prefs and it will show you right there. 2 clicks.

 

[Nothinman]

I hope that last post was a joke.

 

[skyking]

me too.

I need to spoof a mac address on the WAN interface of a linux firewall box. I have never tried something like that in config files. it will be a dhcpd interface, but if i get that MAC right I will still have my old IP.
This comes in handy, since I have my current IP in several servers as an allowed host for various services.
If I just toss the box together and leet the thing grab any old address, i will have a lot of files on remote sysetms to fix.

 

[Boscoh]

When I read that post, I laughed out loud. The people in the library looked at me like I was nuts.

Anyways, this should help you figure out how to change your MAC.
http://www.nthelp.com/NT6/change_mac_w2k.htm

 

[skyking]

That looks like a link for a win2k/xp fix, if I am not mistaken. I am looking for linux answers, but thanks anyway

 

[Nothinman]

Most distributions have hooks for running commands before bringing an interface up, you most likely just need to find it and run 'ifconfig eth0 hw ether 01:02:03:04:05:06' before running dhcpcd, pump, etc.

 

[skyking]

found this googling

spoofing max at ifconfig-up