hai alll
I have a question.I asked it to many people but o one can give a correct reply
the question is "why we have unique mac address when we have ip address which is uniuqe in a network.?
Most people answered that it is for portablity with older systems .is it true?

This might answer your question.

Keep in mind that not all comms run over TCP/IP

Hi,

Of course IP address are unique on a network, but that's not enough so as to identify a machine.
IP address are unique but not dedicated to a host. Most networks use dhcp, which means that IP address can belong to any computer !!!
The real issue, is that, when a network adapter sends a packet, the only way to tell that he is the sender is that he puts its own address in the packet. But since IP address can change from machines (and from NIC), then there must be an address specific to the NIC : that's the use of a mac address for ethernet.

What's more, some devices (cameras, prodcution machines) do not use IP, since it's a layer above ethernet that may not be needed. Another exemple : when you first configure some network adapters (as a matter of fact Linksys WET54G --- which is a real ******) you have to address them through ethernet so as to be able to give them an IP config.

Well, back to work !

Of all the network equipment
Only routers can read the IP address from a given Packet & then route it accordingly


Switches [ most commonly used ]
divert traffic based on the mac address..


you mite want to read about the 7 Layer OSI model for network communication
to get a clear understanding how how packets actually reach their destination

That's interesting because if you asked someone who was familiar with networking they should be able to give you a better answer.

Everyone else seems to have answered your question, or provided helpful information/links so I'll just generalize and say that systems on a global network, like The Internet, use your IP address to find your system because they can group IP addresses into subnets to more easily find where in the world you are, while computers on a local network use the MAC address to distinguish the different computers plugged into the same hub/switch/router. Both addresses are needed because the MAC address distinguishes you on the Ethernet network you are plugged into while the IP address distinguishes you on The Internet, which has more than just Ethernet networks on it.