Convince me that Ethernet is Layer2 only

[DragonNOA1]

I have to convince a prof that ethernet is only layer 2 and not layer 2 & 3. Everywhere I look it says nothing about ethernet having to contain layer 3 info. For example, a 10base2 network running NetBeui (which doesn't even have a layer 3 protocol). Can anyone back me up on proving that ethernet does not have to operate at layer 3?

 

[ktwebb]

Ethernet lives at layer 1 and 2, physical and Data Link layers.

Just google ethernet OSI model. Too many links to links that will give you this information. Layer 3 protocols simply use ethernet as a transmission medium.

 

[BobSutan]

Your question... it boggles the mind. How do you prove there is no such thing as purple-polka dot elephants if nobody has ever seen one before? Its plain old fashind false logic. Ah, the ploys of higher education.

ktwebb hit the nail on the head. Its Layer 1 & 2. Period. IEEE, OSI, and a few other engineering and acedemic entities say so. There's really no other way of puting it.

 

[PHUNBALL]

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[moetop]

Here's a good site to start with.

Personally I would get a couple of old crappy Cisco switches that can run CDP, connect them together, and sniff the traffic. CDP run's at layer 2 (MAC address only). You will see traffic without any ip addresses, You should also see some spanning tree (If it's turned on). You can pull the packet apart to show no layer 3 type headers. And to prove it works, you can do a "show cdp nei" and you will see the neighbor without any layer 3 running.

If he wants proof that should give it to him.. I would be wary of just quoting a bunch of IEEE, and OSI stuff, because I suspect he is either looking for an argument or a long discussion. Unless this is an assignment, then maybe he wants a bunch of BS on paper.

I always like to go for the working demonstrations when people ask me baited questions.


EDIT: Heck for that matter fire up a sniffer on the school network and you will probably see layer 2 packets.

 

[Xipher]

Ethernet may contain information about was is going on above it (what they layer 3 protocal is for each packet) but it does NOT DEFINE those protocols, and can be used idependent of them.
It actually doesn't even require any protocol to be riding ontop of it, but then the data probably won't be routable.

To put it simply, ethernet does not define any properties of layer 3, and doesn't even care about any thing outside of the LAN. Once you hit a router, the ethernet data is scraped away, yet the layer 3 data (IP, IPX, any other protocol the router can route) still exists and is vaild.

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