NIC operation level (Network+)
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When a device grabs an IP, is it not assigned to the NIC? IF the NIC operates at level 2 then why does our device need an IP?
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Bobby,
You're asking a great question! Think about it this way. When you have to get from where you are to where you want to go, you need two pieces of information: You need to know where you're going ( destination) and you need to know how to get there (provided directions).
You or I might pick a vacation destination and then choose to go on the interstate highway and take these turns, etc.
Data that is prepared for delivery has to have both too. On the package we include the destination where the package is ultimately going (IP address) and it needs a MAC address so that the data can be moved from location to location until it reaches the destination.
Software is used to say where the data should go. It normally uses IP addresses. Then when the computer is ready to put the data on the wire it tries to link the IP address to a device by MAC address (ARP)
Cordially,
Ronnie Wong
Host, ITProTV -
So why not just use the router's WAN IP for internet routing and use only MAC addressing on the internal network? Is it just for the convenience of managing the network since they're easier to remember than MACs? I doubt this is relevant for the certification but I'm just curious. Thanks for the quick reply!
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Bobby,
Two things. Since the IP address is just an address on the packet, it does nothing to "forward" or move the data. It really just helps the device know whether the data has arrived at it's proper destination.
To move the data, it must move from device to device; this is what the MAC address on the data frame does. As data is put onto the wire, devices that see the frame must process the Layer 2 address first to see if the data belongs to that device. If the MAC address on the frame matches that of the NIC it was received, then it is processed and moves to Layer 3, the IP address. If the IP address on the packet, matches the IP address of the device, then the Layer 3 adddress is processed and the data has reached it's final destination.
But what can and does happen, The first hop along with many other hops in the path to that destination is not the final destination of the packet. On the LAN, the originator of the data will put source and destination IP address on the packet, then Layer three will request of ARP to find a matching MAC address to that destination IP address. If it does, then all is good, and the data is forwarded there. But let's say that the IP address is destined for another network. It doesn't know the MAC address to the destination. That would normally mean the packet cannot be sent. Except that your machine has a default gateway IP address. So layer 3 substitutes the MAC address of the Default Gateway and links it to the Destination IP address on the original sender's packet.
The data is put onto the wire, When the router (default gateway) processes the frame that has arrived. It will process the Layer 2 address and see that the frame belongs to him. When the Layer 3, processsing happens the destination IP address on the packet will not match the IP address on the router, the Layer 3 will not be processed. The router will take over and try instead to find a route in it's routing table that will match the NetworkID of the packet.
When the router finds a route, it will take the packet, and package it back into a frame to forward it to it's next hop (router). It already has the MAC address cached for that next hop. So the router will now replace the destination MAC address with the next hop MAC address and forward it to the next router along the path to the destination. This will continue to happen until that frame ends up on the device that has the same MAC address and the same IP address. Then and only then, will the data be delivered to it's destiantion.
So you see that data has to be properly addressed with an IP address so it knows it's at it's destination or not. It also relies on a Layer 2 address (MAC) to be able to move the data on it's path to the destination.
Cordially,
Ronnie Wong
Host, ITProTV -
Bobby,
Two things. Since the IP address is just an address on the packet, it does nothing to "forward" or move the data. It really just helps the device know whether the data has arrived at it's proper destination.
To move the data, it must move from device to device; this is what the MAC address on the data frame does. As data is put onto the wire, devices that see the frame must process the Layer 2 address first to see if the data belongs to that device. If the MAC address on the frame matches that of the NIC it was received, then it is processed and moves to Layer 3, the IP address. If the IP address on the packet, matches the IP address of the device, then the Layer 3 adddress is processed and the data has reached it's final destination.
But what can and does happen, The first hop along with many other hops in the path to that destination is not the final destination of the packet. On the LAN, the originator of the data will put source and destination IP address on the packet, then Layer three will request of ARP to find a matching MAC address to that destination IP address. If it does, then all is good, and the data is forwarded there. But let's say that the IP address is destined for another network. It doesn't know the MAC address to the destination. That would normally mean the packet cannot be sent. Except that your machine has a default gateway IP address. So layer 3 substitutes the MAC address of the Default Gateway and links it to the Destination IP address on the original sender's packet.
The data is put onto the wire, When the router (default gateway) processes the frame that has arrived. It will process the Layer 2 address and see that the frame belongs to him. When the Layer 3, processsing happens the destination IP address on the packet will not match the IP address on the router, the Layer 3 will not be processed. The router will take over and try instead to find a route in it's routing table that will match the NetworkID of the packet.
When the router finds a route, it will take the packet, and package it back into a frame to forward it to it's next hop (router). It already has the MAC address cached for that next hop. So the router will now replace the destination MAC address with the next hop MAC address and forward it to the next router along the path to the destination. This will continue to happen until that frame ends up on the device that has the same MAC address and the same IP address. Then and only then, will the data be delivered to it's destination.
So you see that data has to be properly addressed with an IP address so it knows it's at it's destination or not. It also relies on a Layer 2 address (MAC) to be able to move the data on it's path to the destination.
Cordially,
Ronnie Wong
Host, ITProTV -
Thank you for the thorough response. Learning tons on here.
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Robert,
Glad to answer questions so that you can get the answers you need for success! Just let us any other questions we can help answer for you. Also of course, tell a friend! :)
Cordially,
Ronnie Wong
Host, ITProTV