How does maliciously changing IP and MAC address disrupt other's connectivity?

Hey guys, could you give me a explaination of how would a user maliciously altering their IP or MAC address be able to disrupt another user's network connectivity?How does maliciously changing IP and MAC address disrupt other's connectivity?
Ok, first thing you need to know is, that everyone on the internet (that is directly connected to the internet, and not behind a NAT routed network) has a unique IP address that no other person can have at that time. The same applies for MAC addresses.



Each piece of networking media has a MAC address to uniquely identify it on a layer 2 device such as a switch, or in some cases a bridge or router.



If two people have the same IP address in a given network, each user will be notified that duplication has occured, and traffic will not be routed correctly to each device. Routers keep track of various IP addresses, and the ports to which the communications for a given address can be directed to. If there is a conflict, traffic destined for IP address may be discarded until the IP conflict is resolved, no one computer may be allowed to send or receive traffic through the router.



The same thing goes for MAC addresses as well. Most networking equipment have various algorithms to prevent this from happening, but there are some vulnerabilities that do tend to let this happen. When a switch receives a duplicate MAC address, it could destabilize the MAC address table, and cause any number of problems including disrupted network communications to that computer until the conflict is resolved.



The malicious intent behind changing an IP address or MAC address can be for various reasons, some of which is to disrupt communications to a given device, other reasons are to intercept communications for the purposes of man in the middle attacks for theft of data and worse.



There are a number of reasons, and rarely are they good reasons, for doing what you are asking about.