ok.. i just woke up and may be groggy, but what is a layer 2 cable?
*********** REPLY SEPARATOR ***********
On 12/9/2000 at 5:10 PM Gareth Hinton wrote:
>Layer 2 Cat 5 cables for sale.
>All MAC addresses configured identical (to make addressing system easy).
>Anyone interested?
>
>In defence of the people who brought DTE and DCE into the argument:
>
>It was an analogy, a memory aid for the old folks amongst us. Works for me
>(and if I remember rightly, Chuck the elder), so if it confuses or annoys,
>please forget it.
>
>By the way, the layer 2 cables have been withdrawn until further development
>can be carried out. Seems to be some problem with them.
>
>Regards,
>
>Gaz
>
>"John Neiberger" <[EMAIL PROTECTED]> wrote in message
>4179447.976255551441.JavaMail.imail@puffer">news:4179447.976255551441.JavaMail.imail@puffer...
>> There is no DTE or DCE in Ethernet-world. Those are serial communication
>> terms that do not apply here.
>>
>> And hubs are definitely layer one devices, not layer two. To be
>considered
>> layer two, they would have to be aware of layer two addressing schemes,
>> which they are not. They are, however, very aware of the physical
>> necessities of ethernet communication on a 10 Mbps/Half duplex LAN, and
>they
>> do just a bang up job at it.
>> Regardless, there's no topological difference between a 10baseT LAN
>> connected to a single hub, and 10base5 LAN devices connected to a single,
>> long cable. And I hope no one will try to make the case that the cable is
>a
>> layer two device.
>>
>> In Ethernet, your transmit pair must connect to the receiver's receive
>pair.
>> Hub and switch ports are wired internally to be crossover ports, or MDI-X,
>> so that any ethernet hosts connected to it will have their transmit pair
>> connected to everyone else's receive pair.
>>
>> This means that if you connect a hub to a hub, a hub to a switch, or a
>> switch to a switch using a straight cable you are connecting two ports
>that
>> are both crossed-over. This will connect the transmit pair of the first
>> device to the transmit pair of the second, and consequently the receive
>> pairs will also be connected. This obviously will not work! That is why
>if
>> one of these devices is a hub with an MDI/MDI-X switch, you would set it
>to
>> MDI to undo the internal crossover. This matches up the pairs correctly
>and
>> communication will proceed.
>>
>> If you have two switches, then you have no MDI/MDI-X button to press and a
>> crossover cable is required to match up the transmit and receive pairs
>> correctly.
>>
>> I hope that makes sense. As usual, I need to go to bed and get some rest.
>> I tend to ramble when I'm sleepy...
>>
>> Zzzzzzzzzzzzzzzz,
>> John
>>
>> > DTE to DTE uses cross-over cables.
>> > Is this correct?
>> >
>> >
>> > ""Bradley J. Wilson"" <[EMAIL PROTECTED]> wrote in message
>> > 031901c0608a$b9d87d20$ca01010a@bwilson">news:031901c0608a$b9d87d20$ca01010a@bwilson...
>> > > Okay...I've been digesting the responses I've received about this
>> issue,
>> > and
>> > > what I've come up with can be reduced to two comments:
>> > >
>> > > 1) The fact that flipping the MDI/MDI-X switch didn't initially work
>> leads
>> > > me to believe that I wasn't using it right. The fact remains that
>> > > connecting a hub to a switch must be accomplished using a crossover
>> cable.
>> > >
>> > > 2) Why is that? It's true that connecting devices at different
>layers
>> of
>> > > the OSI model requires a straight-through cable, and that connecting
>> > devices
>> > > at the same layer requires a crossover cable. So isn't it true that
>> > > switches are layer 2, and hubs are layer 1? No. Hubs are actually
>> layer
>> > 2
>> > > devices, and here's why: while a hub may not understand or care about
>> > source
>> > > and destination MAC addresses, checksums, or what's in the "type"
>> field,
>> > it
>> > > *does* know the rules of CSMACD communication, and has to play by the
>> same
>> > > rules as other layer 2 devices. Therefore, hubs can be considered
>> Layer 2
>> > > devices, and thus must be connected to switches with a crossover
>cable.
>> > >
>> > > Anyone see anything wrong with my synopsis above? Let me know. Just
>> be
>> > > careful with your caps lock key. ;-)
>> > >
>> > > Thanks,
>> > >
>> > > BJ
>> > >
>> > >
>> > >
>> > >
>> > > _________________________________
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>>
>>
>>
>>
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