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-   -   Same MAC for Multiple computers on same network (https://www.linuxquestions.org/questions/linux-newbie-8/same-mac-for-multiple-computers-on-same-network-4175597890/)

zaheerabbas1988 01-20-2017 10:35 AM

Same MAC for Multiple computers on same network
 
Can i run multiple computers/servers having same MAC address on same network?? Is it possible in centos or any other distro?
Any help in this regard will be highly appreciated.
Thank you

Rickkkk 01-20-2017 11:59 AM

No - your switch would not accept the conflict and either disconnect the currently connected computer before connecting the new one or just refuse to connect the new one. My memory ( ... yowch - so long ago ...) of the OSI networking model is that MAC is controlled at the physical sublevel of level 2 ... So it's OS-independant - wouldn't work in any environment.

I'm curious, though, under what conditions would you want this to happen ? I assume you're talking about virtual machines, since no 2 network interface adapters / chips would have the same physical MAC address.

JeremyBoden 01-20-2017 12:15 PM

See http://xmodulo.com/spoof-mac-address...ace-linux.html
For physical MAC address spoofing.
I've not tried it.

Note that IPV6 (as implemented by some ISP's) incorporates your routers internet facing MAC address into the internet IP address.

suicidaleggroll 01-20-2017 12:50 PM

I've used some embedded systems with software defined MAC addresses, right out of the gate they're all defined with the same MAC. It's a networking nightmare until you split them up. It has nothing to do with the OS running on the system.

rtmistler 01-20-2017 12:57 PM

Yes you can change your MAC address, however as pointed out, having them on the same network will cause conflicts.

The MAC address is the physical address as far as the network cares. Literally CSMA-CD is used where a frame is sent to that physical address and CSMA-CD means "Carrier Sense Multiple Access, with Collision Detect" where the address in question which responds first to the frame for it, will then result in the device obtaining network bandwidth in order to talk. Thus you'll have conflicting devices attempting to speak on the line at the same time. This will not be helpful for your network, it will be a very blocking issue due to interference from all the duplicate stations.

Look up how MAC physical access works in networks.

zaheerabbas1988 01-22-2017 11:39 AM

Quote:

Originally Posted by Rickkkk (Post 5657852)
I'm curious, though, under what conditions would you want this to happen ? I assume you're talking about virtual machines, since no 2 network interface adapters / chips would have the same physical MAC address.

We have purchased very costly software for one MAC only, so the idea is to run it on multiple computers on the same network with same MAC but different IP addresses for test purpose.

zaheerabbas1988 01-22-2017 11:43 AM

Quote:

Originally Posted by JeremyBoden (Post 5657860)
Note that IPV6 (as implemented by some ISP's) incorporates your routers internet facing MAC address into the internet IP address.

We are currently using this method of MAC spoofing, and using this technology now two computers on our offline-network (Not connected to internet) having same MAC. Is there anyway to run them both on same Network without messing the whole network?

zaheerabbas1988 01-22-2017 11:46 AM

Quote:

Originally Posted by suicidaleggroll (Post 5657867)
I've used some embedded systems with software defined MAC addresses, right out of the gate they're all defined with the same MAC. It's a networking nightmare until you split them up. It has nothing to do with the OS running on the system.

Can you play explain this in a little bit detail, as my problem is i have purchased license for 1 MAC only, but i want it to run it on 2 MAC addresses on the same network, is there any way to achieve that goal?

zaheerabbas1988 01-22-2017 11:53 AM

Quote:

Originally Posted by rtmistler (Post 5657873)
Yes you can change your MAC address, however as pointed out, having them on the same network will cause conflicts.

The MAC address is the physical address as far as the network cares. Literally CSMA-CD is used where a frame is sent to that physical address and CSMA-CD means "Carrier Sense Multiple Access, with Collision Detect" where the address in question which responds first to the frame for it, will then result in the device obtaining network bandwidth in order to talk. Thus you'll have conflicting devices attempting to speak on the line at the same time. This will not be helpful for your network, it will be a very blocking issue due to interference from all the duplicate stations.

Look up how MAC physical access works in networks.

Lets say my Computer is originally having MAC (A) but i want it to use MAC (B) because i have purchased license for this MAC but the problem is there is already a computer using MAC (B), so definitely my switch will create alot of networking problems for me if i put them both on the same network at the same time. Because switch use MAC addresses for data transmission.
Is there a way to bypass this, i mean can i use two MAC addresses, original MAC MAC (A) to pass my traffic to the switch without causing any network issues and MAC (B) to run my software at computer level?

JeremyBoden 01-22-2017 12:25 PM

https://en.wikipedia.org/wiki/Addres...ution_Protocol
has a some details on how a network uses MAC addresses.

273 01-22-2017 12:31 PM

I would suggest asking the people you bought the software from whether it's possible to have an evaluation copy at either no cost or a lower cost. If it's possible that you'll end up purchasing more copies depending upon the results of your tests they should want to accommodate you in order to win future business.

zaheerabbas1988 01-22-2017 01:01 PM

Quote:

Originally Posted by 273 (Post 5658640)
I would suggest asking the people you bought the software from whether it's possible to have an evaluation copy at either no cost or a lower cost. If it's possible that you'll end up purchasing more copies depending upon the results of your tests they should want to accommodate you in order to win future business.

I have talked with their support team, they are asking for to buy full license which is about 60K $. So...

273 01-22-2017 01:06 PM

Quote:

Originally Posted by zaheerabbas1988 (Post 5658652)
I have talked with their support team, they are asking for to buy full license which is about 60K $. So...

Hmm, sounds a little unreasonable behaviour towards a potential customer, shame you can't go elsewhere.
If you're willing to buy a router or have one lying around you might be able to get away with having the same MAC address on two devices if they're on different LANs since the router will move packets based upon IP subnet and not MAC address like a switch would.

michaelk 01-22-2017 01:17 PM

Is there a license agreement that you are only allowed to run the program on one computer only or one computer on the network? I assume the software company is using the MAC as some form of licensing measure and I consider this a violation of the LQ rules.

Quote:

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BW-userx 01-22-2017 01:34 PM

wouldn't having the same MAC for two or more be an violation of Logic? (for lack of better term)
Because a MAC address is just that an address. it is like a address to a house, if two houses have the same address then a confusion is a result of it because one would not know which house is suppose to actually get the mail.

If the intent is to confuse a receiver when it asks, where did this come? then having to trace back to find out. Well then ....


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