MAC address are similar result in similar ip address

By using "a-change MAC address V5.0", I did a test within same LAN, I have got two laptop A and B with Nortel Acess Point.

These laptop are getting IP address form Nortel AP automatically. Type of ip address is 10.70.72.x/24.

IP address for laptop A is 10.70.72.93/24, and MAC is 00-91-4C-2A-2B-2C.

IP address for laptop B is 10.70.72.141/24, and MAC is 01-80-4C-29-22-29.

I changed the MAC address for laptop B to be same to laptop A (i.e. form 01-80-4C-29-22-29 to 00-91-4C-2A-2B-2C ).

When I changed the MAC address , ip address for B has been changed to be same to the ip address for A as well,,,,,Why ? What is concept ? does it related to ARP protocol ?

I have not received notification message telling me that the are conflict in the ip addresses.

If laptop A tries to access the net first , then Laptop B can not access.

And if laptop B tries to access the net first , then laptop A can not access the net.

I tried to change ip addresses for one of the laptop , and keep MAC address similar for both of them, by configure laptop A manually with existing any ip address within the same LAN (i.e 10.70.72.141/24 has not been assigned to other PC within LAN) ),,,,,result still same I can not

zillah, you cannot have two different devices with identical MAC addresses in the same subnet. Therefore you will need to ensure that your laptops have different MAC addresses.

you cannot have two different devices with identical MAC addresses in the same subnet.

Yes I am aware of that. But i am asking why they getting same ip address and why they are not receiving error message for conflict message when they get same ip ?

Because they have the same MAC address and they appear to be the same computer to the rest of the network ...

they are getting the same IP address as the ARP is finding the same MAC address, and the subsequent resolution is giving out identical IP addresses. withing the same network no two machines should have the same MAC addresses. this is for the simple reason that the MAC address is the most vital address for differentiating between machines within the same network. had it been between two different network, for which the IP address is most vital, having the same MAC address on different networks wouldn't cause any trouble. but on the same network, when a packet arrives from an external network, the ARP maps the IP address of the destination address to its corresponding MAC address. for two pc's having the same MAC address, ARP will be mapping it for two pc's, and randomly either of the pc's will be receiving all the traffic meant for the IP address. so its obvious, that either of the PC's will be receiving all the traffic, and the other one wont.