Ethernet and MAC addresses

zobo88

Are Mac addresses only used by Ethernet ?
and what are other competing data link protocols to Ethernet ?

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N3tWrkNut

There are many layer 2 protocols.....frame-relay, HDLC, FDDI, PPP does that answer your question?

zobo88

N3tWrkNut wrote: »

There are many layer 2 protocols.....frame-relay, HDLC, FDDI, PPP does that answer your question?

thanks
so MAC addresses are only used by Ethernet ?

peanutnoggin

Mac Addresses are used by Network Adapters or more commonly... NICs. But I believe that any device that can get "network connectivity" has a mac address such as a cell phone connecting to a 3G network, etc... I hope this helps.

V/r

~Peanut

Jonk

zobo88 wrote: »

thanks
so MAC addresses are only used by Ethernet ?

Do you mean does the computer use the MAC address of its NIC for any other purpose? I do not believe so.

daveccna

zobo88 wrote: »

Are Mac addresses only used by Ethernet ?
and what are other competing data link protocols to Ethernet ?

I could be wrong but I thought that anything operating on layer 2 would require the MAC address. Anytime you send information on a LAN you're building a frame and using MAC to address it.

Ethernet is layer 1 and defines the specification of the physical medium (ie copper and pin outs) and signalling rules like CSMA/CD.

I'd associate MAC addresses with ARP rather than ethernet.

EDIT: Wiki is your friend...

http://en.wikipedia.org/wiki/OSI_model

Jonk

daveccna wrote: »

I could be wrong but I thought that anything operating on layer 2 would require the MAC address. Anytime you send information on a LAN you're building a frame and using MAC to address it.

Ethernet is layer 1 and defines the specification of the physical medium (ie copper and pin outs) and signalling rules like CSMA/CD.

I'd associate MAC addresses with ARP rather than ethernet.

EDIT: Wiki is your friend...

OSI model - Wikipedia, the free encyclopedia

Yea I was thinking that as well with the data link layer.

dummy123

first, what are mac addresses for? pretty much to find a computer on the same lan as there's a bunch of other hosts so the sending pc needs to make sure data goes to the right pc.

not all layer 2 protocols are for lans..
ppp and hdlc are examples of point to point l2 protocols.

R1 <

HDLC/PPP

> R2

there are only 2 points, so mac address is not needed.

correct me if i'm wrong.

daveccna

dummy123 wrote: »

first, what are mac addresses for? pretty much to find a computer on the same lan as there's a bunch of other hosts so the sending pc needs to make sure data goes to the right pc.

not all layer 2 protocols are for lans..
ppp and hdlc are examples of point to point l2 protocols.

R1 <
HDLC/PPP
> R2

there are only 2 points, so mac address is not needed.

correct me if i'm wrong.

According to this it does...

PPPoE discovery

Since traditional PPP connections are established between two end points over a serial link or over an ATM virtual circuit that has already been established during dial-up, all PPP frames sent on the wire are sure to reach the other end. But Ethernet networks are multi-access where each node in the network can access every other node. Ethernet packets contain the hardware address of the destination node (MAC address) encoded in the packet. This helps the packet reach the intended destination.
Hence before exchanging PPP control packets to establish the connection over Ethernet, the MAC address of the two end points should be known to each other so that they can be encoded in these control packets. The PPPoE Discovery stage does exactly this. In addition it also helps establish a Session ID that can be used for further exchange of packets.

cite
Point-to-Point Protocol over Ethernet - Wikipedia, the free encyclopedia

Which makes sense to me because although it's essentially a network with only two nodes it's still going to look at the frames it's receiving.

dummy123

that just proves my point. until you encapsulate ppp with ethernet (pppoe), it doesn't use mac addresses...

zobo88

dummy123 wrote: »

first, what are mac addresses for? pretty much to find a computer on the same lan as there's a bunch of other hosts so the sending pc needs to make sure data goes to the right pc.
.

Thanks
That leads me to another question
why does a Switch needs to have MAC addresses of its own ?

Bl8ckr0uter

zobo88 wrote: »

Thanks
That leads me to another question
why does a Switch needs to have MAC addresses of its own ?

Ok this is very, very important. Are you studying for any kind of cert exam (CCENT, CCNA NEtwork+) because I can tell you if you are, you will need to know this. It could very easily be explained but it is going to be better if you read it yourself. Pick up Todd Lammel CCNA study guide or google a bit. No offense....

Bl8ckr0uter

And like others have said, MAC address are defined at layer 2 by the ethernet standard.

hexem

Know ethernet and mac addresse's well, especially how a switch handles and deal's with incoming frame's and how it uses the source mac address and destination addresse's when fowarding frame's on.

Anything involving the data link layer is usually using MAC addresse's when were talking about Local area network's, just remember the data link layer address type may change for differn't encapsulation's, such as frame-relay which uses DLCI addresses.

and as to your question on why switche's have mac addresse's, if they didn't there would be no inter-switch communication between device's, when sending frame's for thing's such as STP/VTP/CDP and being able to remotely manage a device etc ;] hope that helps.

Bl8ckr0uter

hexem wrote: »

and as to your question on why switche's have mac addresse's, if they didn't there would be no inter-switch communication between device's, when sending frame's for thing's such as STP/VTP/CDP and being able to remotely manage a device etc ;] hope that helps.

I was going to say something more general like, it would not comply with ethernet's layer 2 standards without one.....