How do we fix this problem? by using a hieracrchial addressing structure, ip is the solution, layer 2 addresses i.e. Now as time goes by we add more and more devices and soon the switch is fully populated,now we add another switch and another and soon we have too many to count.The mac-address table on the switches get bigger and bigger and the length of time to do a table look up gets longer and longer, soon the end applications will timeout and send the frames again.So we have a hugh mess. Lets look at the scenario with only mac addresses.Mac addresses are layer 2, before sending a layer 2 frame my pc needs to add a source and destination mac-address.When this frame is sent,every other device on the wire must examine this frame to see if the destination mac is addressed for it.This means the more devices i add to the local wire the more flooding, soon your pc nic will spend all its time looking at unwanted frames and have no time to receive frames destined for it.Now you decide to fix the problem with a switch,this means every device is on its own wire a the switch will map mac addresses to ports so the flooding problem is over. Whats the point of having a logical IP address? When the packet already contains the MAc address tehn why does it ahve to ahve an IP address as well. I am new so maybe my questions sound dumb. Hmmm so instead of all this why dont people jsut communicate on the internet using their MAc addresses? They would be represented as individual hosts on the internet instead of all this translation and routing business. The ARP table will tell the router its internal IP and it can then send that information to the correct computer on the LAN. When the packet comes back to the router by using the public IP instead of the internal IP, it can take the MAC address that was still stored in the packet information and look at its ARP table. What the router does is strips the internal IP address (192.168.0.100 or whatever) and will put the public IP address of the router in its place ( But in layer 2 it will continue to store the MAC address of the computer while passing traffic to the internet. When computers want to pass traffic to the internet, it will pass through the router. When you have a router at home, it runs network address translation to be able to use 1 IP address for multiple computers in a LAN. So hopefully to give an example where both are used will help. But if I were asking this question, it would help me a lot to know something that uses both technologies. Remember, every NIC has a unique MAC address. MAC addresses also are just used to identify the actual NIC. MAC addresses do not have the ability to be subnetted.
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