Same IP and MAC address in same network.....

[Ranajitnath7]

I am in beginning in CCNA... My teacher told me that, In one network Same IP or Same MAC ID not connect in network.... But its working ..... If i get your response, i can show you..... Sorry, For my bad english....   

[Ben Gartland · Accepted solution]

It may look like it works in a small lab, but trust what you're told, it does not work.  

It WILL cause error messages on devices with duplicate addresses.

As soon as you try sending traffic between hosts:
It WILL cause switching and routing problems on your network.
It WILL cause packet loss on your network.

Regards,

Ben

[Ranajitnath7]

I can also use PACKET GENERATER... But there are no losses in send ICMP pakages....    If you want i can send you .PKT file...... 

[Ranajitnath7]

But it also use for network clone, that is one types of hacking.... Then ??? Security Problem ?

[Ranajitnath7]

PFA.......

[Ben Gartland]

Wireshark can't open that .pkt file for some reason.

If you try this with real equipment, 2 LAN hosts and a switch, you will see all sorts of issues.  Not only duplicate IP addresses, but the switch will not know how to direct the frames as the same source MAC will be see on 2 different interfaces.

[pwwiddicombe]

In a "structured laptop build" we had at one time, IBM had changed the Ethernet driver; but the techs merrily continued as before.  Builds worked, Ethernet connectivity worked (apparently).

However, they would randomly disconnect.  Turns out using the wrong Ethernet driver wound up giving all workstations of that model the SAME MAC address.  As long as they were on different subnets, there was no apparent issue; but having several on the same one led to all sorts of mysterious/random disconnections.  When it happened, the user would reboot, and ANOTHER (with the same MAC) would lose connectivity.