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IP address and MAC address question

Hi there,


I need some help with the following concepts:


1) summarize what happens to IP addresses as they traverse the network


2) summarize what happens to MAC addresses as they move through the network


3) describe what happens to MAC addresses and IP addresses as they pass through switches


4) describe what happens to MAC addresses and IP addresses as they pass through routers


THANKS A LOT!

- Greg

1 REPLY
New Member

IP address and MAC address question

Hi Greg,

1) summarize what happens to IP addresses as they traverse the network


Nothing happens to IP address as they traverse the network. The IP addresses (Source & Destination) remain same in the entire communication. The communication may be in the same subnet or with the other subnet.

2) summarize what happens to MAC addresses as they move through the network

As you might already know that the MAC is a layer2 address.

The Address resolution protocol resolves the IP address to the MAC addresses.

Communicating to a device Within the subnet: The MAC addresses in the frame remain same.

Communicating to a device in other subnet: The default gateway put its MAC address in the Source field to get you to the destination, in both the directions.

3) describe what happens to MAC addresses and IP addresses as they pass through switches

Switch don't modify the layer2/layer3 address, their duty is to learn the MAC address from the incoming frames and map them to the associated port, just for the intelligent forwarding of the traffic based on the MAC addresses.

4) describe what happens to MAC addresses and IP addresses as they pass through routers

     As i already mentioned in the answer for the second question. The IP addresses of the Source and destination devices remains same throughout the communication. But when you're trying to communicate with the device in other subnet, the source device will take the help of the default gateway (router/layer3 switch) to reach the destinaion network and destination device.

Coming to MAC address: MAC address also remain same if the communication is going on b/w the devices in the samesubnet.

While speaking to device in other subnet:

     The default gateway will put its interface (to which your destination device is connected) MAC address in the source field. Same thing happens in the reverse direction.

If you need to understand more about this, then you just go through ARP (Address Resolution Protocol).

And if your intersted to see the frame processing of a switch practically frame-by-frame, just navigate to the below URL

http://network-addicts.blogspot.in/2014/02/working-of-switch-explained-practically.html

Please Don't forget to rate the posts that are helpful.

Regards,

Chandu

Regards, Chandu
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