pl read the question and tell me the best answer?

Question

explain the term ARP Posoning and discuss how it maybe employed to circumvent some of the inherent security provided by a swithced network architecture.

Answer 1

in brief
ARP poisoning enables local hackers to cause general networking mayhem. Because it's mostly "incurable," every administrator should be aware of how this attack works.
ARP, a very simple protocol, consists of merely four basic message types:

An ARP Request. Computer A asks the network, "Who has this IP address?"

An ARP Reply. Computer B tells Computer A, "I have that IP. My MAC address is [whatever it is]."

A Reverse ARP Request (RARP). Same concept as ARP Request, but Computer A asks, "Who has this MAC address?"

A RARP Reply. Computer B tells Computer A, "I have that MAC. My IP address is ....
ARP protocol has no way of verifying ARP replies.

ARP Poisoning: the attacker lies to a device on your network, corrupting or "poisoning" its understanding of where other devices are. This frighteningly simple procedure enables the hacker to cause a variety of networking woes
like DOS -denial of service attack
man in the middle attack Mac floading
If you want more read this:
http://www.watchguard.com/infocenter/editorial/135324.asp
or this
http://www.infosecwriters.com/text_resources/pdf/ARP_Poisoning_In_Practice.pdf

Answer 2

Great Ana, Thats the explanation...No one can explain better than this...

Answer 3

i like it