IP conflict

Hi Blunderboy i was not able to understand your question clearly but i am trying to explain you what really happens when you connect INTERNET while in LAN.

While in LAN you might be connected to a computer which acts as server for you to connect INTERNET, in such situation the speed of LAN is divided to all computers but the speed you are able to see on each PC is original undivided link speed that you server PC can attain. A server is connected to every other PC in network by means of router and a switch or hub or both.

A job of router here is to create routing table to the PC for which data is meant for and then route data to it.
Other device device which come to play are hubs and switches. So when you are connected to a LAN, all PC share same IP address that of the main LAN server or server computer so how can the hell data reaches to destination computer without problem.
Here's the solution,
When data is delivered to server PC it sends it to hub or switch, a hub or switch differentiate computers on the basis of Network Interface Card(NIC) ID and not on basis of IP address so when it gets any packet it is delivered to the computer holding NIC ID defined in packet. The NIC id is better known as Media Access Control ID also known as MAC ID of NIC.
A MAC ID Looks something like this,
01-23-45-67-89-ab, 01:23:45:67:89:ab
So each packet holding a single address to single device in a network is known as UNICAST packet and such address is called UNICAST address.

Though hub and switch do the same job there is a little difference. When a hub gets a packet hub hardly cares to whom it is sending data, the data it receives from main link is broad-casted to each and every device available in network, and the device waiting for packet receives packets meant for all devices in network but it identifies packet meant for itself and accepts it discarding all other packets.
But when switch sends data, it maintains a table of device ID for itself so when data packet is received, the packet is delivered to the device whose ID is present in UNICAST address. The protocol which helps differentiate between different MAC addresses is known as Address Resolution Protocol (ARP). Since switch maintains table to deliver data, it is relatively faster than hub and of course costlier also.

I hope that solves your query, if not please feel free to ask. Happy computing.

@Leo
Hey thanx for the nice info u gave. But actually my query is different.

I just want to know how our OS detects that there is an Ip address conflict.?

You might have used internet in some organization where private adressing was there inside campus and Nat device.

Now suppose you and your room mate use same IP address, your windows machine shows a notification like

Windows System Error : Windows has detected an IP conflict. (Something like that).

So i just wanna know how Os detects it ?

Actually your OS doesn't detect any IP conflict its the network monitoring software running on organization server who detects it then notifies your OS connection cannot be completed so your system asks for information using ICMP code 17 i.e ICMP information request and you get IP conflict error on your system. Is that information useful.

LeoActually your OS doesn't detect any IP conflict its the network monitoring software running on organization server who detects it then notifies your OS connection cannot be completed so your system asks for information using ICMP code 17 i.e ICMP information request and you get IP conflict error on your system. Is that information useful.

Hey thanx once again leo.This is really good and very useful information.
1. Can you please tell me which particular server you are talking about. (Is it where NAT is done)
2. example of network monitoring software

Thanx in advance.

sorry if am over questioning.
Since I am newbie so willing to learn.

When you are connected to LAN, the system which serves you for connectivity is server for your LAN. The server holds a software and hardware which is responsible for address translation and the translating devices and software combined known as Network Address Translator. Due to availability of NAT a single IP address can provide millions of connections under itself. Since a packet is encapsulated in another packet the system you want to connect never actually creates true connection with your system. While on such kind of network traffic and activity on each and every single PC available in LAN can be easily monitored by server system. They can even know which site you are watching, which page, which e-mail id which protocol absolutely everything. So if the Administrator is not that gunky shit head and real bad ass he can even get your passwords and files very easily, even applied IPSec wouldn't pay you.

Thanks Leo.
While registering a computer in a network, it will broadcast it's own address details such as MAC, IP Address over the network.
If there is a same IP Address already exists in the same network, then the IP Conflict Error message will be shown to the both computers, which are having the same IPs.

Am I right Leo ?

for details of how to resolve and other basic details see this URL #-Link-Snipped-#

themaskThanks Leo.
While registering a computer in a network, it will broadcast it's own address details such as MAC, IP Address over the network.
If there is a same IP Address already exists in the same network, then the IP Conflict Error message will be shown to the both computers, which are having the same IPs.

Am I right Leo ?

Hi Mask the error message will not be displayed on computer which is already connected with the conflicted IP address, it will appear if some one else want to register with same IP address.

@Leo I know that a NAT software is there in between the server and the clients.Which work is that to convert local addresses to global addresses. and as you mentioned that in LAN systems are specified by their MAC address.So do you mean to say that NAT working is to convert IP to MAC and MAC to IP address...?

@Mohit the scenario so far we discussed applies to a hybrid topology-LAN. And the software that resides to serve IP address is better known as Dynamic Host Control Protocol Client. The server client software identifies each PC by NAT defined IP address when you are in hybrid type of LAN else if your LAN type is not hybrid the hub or switch you use makes your serving PC act as host and all other connected to it as guest. The MAC information is stored in IP packet and in server client if configured so else not. IP data packet arrives to PC severing as host as a packet meant for itself, and by information stored in packet host PC identifies that packet is meant for some PC connected in same network and data gets delivered.

And NAT's job is to only dynamic IP's creation and then serving network connection, practically it assigns an IP then forgets it until any interruption is forwarded about connection drop or termination, so far i know now it doesn't have any facility to store MAC id's unless explicit configuration is made.