NIC OSI question...

Chris Knight

Guys, not sure if this will come up in the exam, however if the exam asks what layer a NIC resides in, should I say Layer 1?
I know it can reside in both layers, physical and data link, however Im unsure...
I dont think the exam will break it down into detail if they ask about the pins on the nic, well that would be in physical and then if you break down the mac address, now your into layer2...
Need some help

sprkymrk

You're correct. The NIC is considered layer 1 while the mac is considered layer 2. If they ask "nic", say layer 1. If they ask "mac" answer is layer 2.

Danman32

I hate when tests ask questions that aren't clear cut.

Some expensive NICs are even layer 3, taking the IP processing into hardware. I think they even go layer 4 and deal with the TCP.

Most NICs at least handle the IP checksum in hardware.

booboo2

The question I had on exam asked what 2 layers did it reside on and of course it is Physical and Data Link. They did not try to trick me on any OSI questions and as a matter of fact there were hardly any on my exam. Seems like they are gearing up for new exams because I had a lot of questions on wireless.

bighornsheep

booboo2 wrote:

The question I had on exam asked what 2 layers did it reside on and of course it is Physical and Data Link. They did not try to trick me on any OSI questions and as a matter of fact there were hardly any on my exam. Seems like they are gearing up for new exams because I had a lot of questions on wireless.

New Network+ exam? I better step things up and get certified...

elathrop

Another little wrinkle is that the physical address is in the Data Link Layer. The answer to the question about Nics is 1 and 2. Remember, the MAC address is part of the NIC. The MAC (physical) address is positively Data Link or Layer 2. Of course, the 1's and 0's outputed from the NIC are Physical Layer.

It would also be helpful to know what 2 layers a Packet Switching Firewall is associated with. Remember, packets are layer 2. What other layer is involved?

Good luck on the test. You got to know your stuff to be ready for it, but it is not nearly as tricky as the OS.

Danman32

Packets are layer 3. Frames are layer 2. IP Packets, ethernet frames.

Webmaster

Oh no, not the old "On which layer is the NIC?" question again, you obviously didn't searched the forums before you posted

And you didn't read my TechNotes either:

A NIC provides operations up to layer 2 of the OSI model. The NIC's interface itself is a Physical layer (layer 1) device, the physical address (also known as MAC address) of the adapter as well as the drivers to control the NIC are located at the Data Link layer's MAC sub-layer. In an Ethernet network for example, every NIC attached to the same segment receive every ‘frame’ to discover the MAC address. Frames that do not match the local NIC’s MAC address are discarded; frames that do match the local NIC’s address are forwarded up the OSI model to the next layer to be processed by the network layer protocol. Obviously, a NIC must be able to interpret the MAC address, hence operate up to the MAC sub-layer of layer 2 of the OSI model.

And if you don't want to take my word(s) for it, I recently noticed Cisco also explictely lists it as a layer 2 device in their courses, as the probably do on their website as well.

As I posted several times in the past, the OSI model is just that, a model, and in reality things don't always fit on or in one layer. Especially at layer 1 and 2.

More importantly, CompTIA is partly to blame for making this a common discussion/question, as they once had a question on the Network+ exam in which they asked you to choose between the two. Had...

elathrop

Thank you, Danman32. I needed to be straightened out on my packets. Also, I said Packet Switching Firewall. I meant, of course, Packet Filtering Firewall. (Oh! dopey me!) What you say is important Net + information: IP Packets, Ethernet Frames.

I'm not saying this question is on the test, but if anyone asks me what two layers a Packet Filtering Firewall operate on, I'm still not sure; 2 and 3? Possibly 3 and 4 because TCP or UDP is involved?

Danman32

A packet filtering firewall is filtering IP packets at the network level, so certainly not layer 2. But as you say, it is also dealing with the ports in either TCP or UDP so layer 4 would be involved. But layer 3 is the stronger choice if you can't pick 4 or had to choose.

!30

plague22 wrote:

Guys, not sure if this will come up in the exam, however if the exam asks what layer a NIC resides in, should I say Layer 1?
I know it can reside in both layers, physical and data link, however Im unsure...
I dont think the exam will break it down into detail if they ask about the pins on the nic, well that would be in physical and then if you break down the mac address, now your into layer2...
Need some help

Maybe remember this one , the NIC is the phisical device which put's bite's on the wire so first Level ...

bighornsheep

!30 wrote:

Maybe remember this one , the NIC is the phisical device which put's bite's on the wire so first Level ...

Webmaster wrote:

A NIC provides operations up to layer 2 of the OSI model. The NIC's interface itself is a Physical layer (layer 1) device, the physical address (also known as MAC address) of the adapter as well as the drivers to control the NIC are located at the Data Link layer's MAC sub-layer. In an Ethernet network for example, every NIC attached to the same segment receive every ‘frame’ to discover the MAC address. Frames that do not match the local NIC’s MAC address are discarded; frames that do match the local NIC’s address are forwarded up the OSI model to the next layer to be processed by the network layer protocol. Obviously, a NIC must be able to interpret the MAC address, hence operate up to the MAC sub-layer of layer 2 of the OSI model.