IP vs. MAC adressing?

Question

When referring to layer 2 (bridges, switches, etc..) and layer 3 (routers) devices, what is the difference between MAC and IP adressing? Because i have read that a layer 2 device decides to forward the frame depeding on the destination MAC adressed, but layer 3 depends on the IP adress. Can you please tell me the difference and what the signifigance is? Thanks for any help

Answer 1

That is the difference, what you just described... basically that switches use destination MAC addresses to forward frames, and routers use destination IP addresses to decide where to forward packets. MAC addresses operate at the data link layer (layer 2) to forward frames on a local LAN (broadcast domain) across switches, and IP addresses come in at layer 3 to make forwarding decisions by the routers, to forward packets to other networks. So for example, a switch uses 48-bit MAC addresses like 08:00:20:3B:4A:56 to decide where to forward ethernet frames (out which switch port) and a router uses a 32-bit IP address like 172.16.100.25 to decide where to forward IP packets.

When a switch receives a frame, it inspects the destination MAC address and decides where (on what port) to forward the frame. If it doesn't know where the destination host is, it floods that frame out all ports. When a router receives an IP packet, it inspects the destination IP address and makes a routing decision on how to forward the packet.

Check out the Wikipedia articles on router and ethernet switch to get some more info...

Answer 2

The MAC address is the unique address burned into the newtork card .usually ethernet .. and is used to identify layer 2 packets.

MAC layer addressing can be used in one's local lan .. and one's local campus. (local area networkinig (lan)) usually only part of a building. It allows the cards to talk directly to each other.

And layer 2 switching can be very fast, because there are fewer options on what is allowed.

IP is the next layer up. IP addresses uniquely identify any device that can send IP packets. the uniqueness of the IP packet is designed for wide area networking (wan) .. for world wide management of devices. Lots more options, and hardware independence.

IP doesn't care what kind of cards you are running. You can run IP over ethernet, token ring, and a spoof proposal of carrier pigons. AS long as the packets get back and forth .. and are retransmited if lost .. then IP works.

These layers are often considered like addressing on envelopes.

This allows each layer of drivers to be self testing and not really depend on the other layers. However for performance sometimes they are all implemented in a lump.

and UDP or TCP is the next layer .. designed for applications to use to move data from application to application. This is where the 10.16.1.2 type addresses come from. These applications are the client server programs we have learned to love.


More info at the wikipedia article.

Answer 3

Hello,

A media access control (MAC) addresses are assigned to every communications device made. This address is the foundation on which all IP addressing and configurations are built. There are four layers. The first is MAC addressing, then IP addressing rides on top of that, then software interfacing, and lastly user manipulations.

IP addresses are software based, meaning they are configurable. MAC addresses are hardware based static (they never change) addresses. There are a few hacks and tricks and hacks you can do to change you MAC, but that is a different story.

Answer 4

The MAC address of an ethernet or wifi device is a unique (wordwide) hexadecimal number that identifies that device.
http://www.webopedia.com/TERM/M/MAC_address.html

An IP address is a unique identifying number on a network.
http://www.howstuffworks.com/question549.htm