ethernet card

Hi I puchased a socket LP-E pcmcia card from an auction site. Unfortunately the socket pcmcia card was supplied with a xircom connectivity cable and it doesn't work. Is it possible to rewire an existing connectivity cable ? I have attempted to use an oscilloscope on an RJ45 cable to see if I can compare the trace on the 'unknown' cable with a 'known good pcmcia card with cable' on the oscilloscope when using the 'ping' command,(but the cable is going nowhere, unterminated) and I find that I cannot get a good result. Can I use an oscilloscope to view the result of a ping command ? What results should I expect on the 8 pins of a RJ45 cable ?

thanx

GC

Reply to
glc
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Ethernet (10--Base-T) using the UTP connector -- only uses pin 1/2 and pin

3/6 ... pin 4/5 are not used to avoid tip/ting POTS possible cross connect mistakes and pin 7/8 also not used to avoid other uses. All covered in the IEEE 10-Base-T, EIA/TIA 568 standards and equivalent EU standards

gb

Reply to
gb

Is that card only 10bt? Most anything made within the last few years is

10/100 which does use all pairs, and you have to use the right signals on each pair for it to work.
Reply to
James Sweet

100 base T and 1000 base T use the same wires. (1,2,3,6). Most modern ethernet transcievers (2 years old or less) don't care if about the wiring of the pair or if the pairs are reversed.

If you are connecting up to a modern hub such as a WiFi router with a built in 4 port hub, then it will probably work as long as you get the correct wires and keep the correct pairs (1,2 or 2,1) and (3,6 or 6,3) no matter which set you connect to the other end.

I have an ethernet port next to my kitchen table so that if I have to work on a computer, I can just plug it in. Since my hub is 10/100 autosensing of direction and speed, I just keep a reversal cable nearby. That way I can use the same cable to connect to the hub, or computer-computer with older computers.

Geoff.

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Reply to
Geoffrey S. Mendelson

You sure about that? My recollection is that Gigabit uses all 8.

Most modern

Not sure what you mean by that. The electronics can't tell whether you (consistently) swap the white+color and color, as long as you keep the pairings intact. But they will certainly balk at mixing a wire from one pair with a wire from another pair.

I guess I'm still unsure what you mean. They're differential transducers, so the difference is what's important.

If by "direction" you mean X vs II, then it's probably a switch. Or do you mean duplex?

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Reply to
CJT

I'll check, I've don't think so, but occasionaly I'm wrong. :-)

Yes, that's true.

All 10/100 hubs are by switches. How else could they adjust the speed?

Geoff.

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Reply to
Geoffrey S. Mendelson

1000BaseT is 2 pair, and most Gigibit uses 2 pair.

If they didn't they couldn't do Power Over Ethernet (PoE) injection on the first pair, 4&5 B)

RwP

Reply to
Ralph Wade Phillips

I Google'd for it, and this is the first reference I found. But I'm fairly certain I've read it elsewhere, too, including in a textbook on networking:

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Not so. They can adjust the speed just as a switch does. The main difference is that a hub lacks the logic to be selective about where it forwards packets, and as a result doesn't need to maintain tables of MAC addresses.

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Reply to
CJT

Can you offer a cite?

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Reply to
CJT

FWIW, here's a cite with a little more impressive credentials:

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Reply to
CJT

Figure 7 of the cisco site shows all four pairs in use.

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Reply to
P. Thompson

Precisely my point.

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Reply to
CJT

I can say with certainty from experience that 10bt uses only two of the pairs, but 100bt and gigabit both use all four pairs. You have to make sure you use both wires from the same pair for each set of signals too, if you mix and match it doesn't work for 100 or gig, but 10 is slow enough that it doesn't seem to matter for short runs.

Reply to
James Sweet

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I believe 100 uses only the same two pairs as 10. Only when you move to gigabit are all 4 pairs used. Refer to the pages cited. My understanding is that all four pairs must be present anyway, in order for a cable to meet specs (I suspect that's to maintain distances within the bundle, which could affect crosstalk). But for 10/100, only half the wires are connected to anything.

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Reply to
CJT

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INCORRECT, when the 100 Mb standard was being developed there were other proposals that did call for all four (4) pairs to be used. One argument 10 years ago -- that many installations (wiring closet to PC desktop) were not compliant with EIA/TIA 568 (1992)-- and added undue cost in rewiring these installations.

The referenced Cisco web page references the IEEE standards on which these network solutions operate.

As Figure 7 shows, 1000BASE-T (1 Gb) works by using all four of the Category

5 pairs to achieve 1000 Mbps operation over the installed Category 5 copper cabling. 1000 Mbps data rates are achieved by sending and receiving a 250 Mbps data stream over each of the four (4) pairs simultaneously (4 X 250 Mbps = 1 Gbps).

In contrast, 100BASE-TX uses two (2) pairs: one to transmit and one to receive. Fast Ethernet on Copper (100BASE-TX) achieves 100 Mbps operation by sending encoded symbols across the link at a symbol rate of 125 Mbaud.

Some in summary 10/100 Mb Ethernet solutions use 2 pairs and 1 Gb Ethernet uses 4 pairs. All running on an EIA/TIA 568 compliant physical infrastructure.

gb IEEE member Standards Communications

Reply to
gb

Power over Ethernet has TWO OPTONS It can work on the 2 spare pairs with 10 and 100 Mb Ethernet (which uses 2 pairs and has 2 spare pairs) OR on 2 data pairs when used with 1 Gb Ethernet (which uses ALL 4 pairs). Read it yourself.

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Part 4: How Power is Transferred Through the Cable

A standard CAT5 Ethernet cable has four twisted pairs, but only two (2) of these pairs are used for 10BASE-T and 100BASE-T.

The specification allows two options for using these cables for power, shown in Figure 2 and Figure 3:

a.. The spare pairs are used. Figure 2 shows the pair on pins 4 and 5 connected together and forming the positive supply, and the pair on pins 7 and 8 connected and forming the negative supply. (In fact, a late change to the spec allows either polarity to be used). b.. The data pairs are used. Since Ethernet pairs are transformer coupled at each end, it is possible to apply DC power to the center tap of the isolation transformer without upsetting the data transfer. In this mode of operation the pair on pins 3 and 6 and the pair on pins 1 and 2 can be of either polarity.

gb

Reply to
gb

Simple question on your excellent response which answers the 2 pair vs. 4 pair question:

100BaseT is 100Mbps full duplex. This means it can pass 100Mbps in both directions simultaneously. This is done by using a pair of wires in each direction (uplink=send/downlink=receive). You indicate that GbE is a full 1000Mbps and uses the 4 pairs which each send 250Mbps. Does this imply that GbE is now half duplex or that the send uses 2 pairs and the receive another pair? What is the maximum SIMULTANEOUS transmission rates in the uplink and downlink? Can you provide some insight since I had always assumed GbE was also 1000Mbps full duplex like 100BaseT Fast Ethernet.

Thanks in advance for your insight here. It is important to understand if GbE is 5 times or 10 times faster than FE.

Bob

Category

copper

by

Reply to
Bob Shuman

Howdy!

injection

You are, of course, right.

That's what I get for "extending from previous learning experiences" ... PoE has always been on pins 4 &5 in my past experience, and I've got at least two customers with 100BaseTX stuff running over PoE connections (webcams, both of them) to a gigabit switch (a Catalyst), with no seperate injector.

Thanks for the education!

RwP

Reply to
Ralph Wade Phillips

Bob -

Excellent question, and I am laughing .. because I was never in favor of using with copper cabling with GbE (I preferred the usage of fiber optic cabling).

I have not participated or even kept up with GbE and the current 10 GbE discussions (and roadblocks) for several years.

1000BASE-T is one (1) of the fours (4) physical layers or transceivers defined by the two GbE (Gigabit Ethernet) standards: IEEE 802.3z or 1000BASE-X and IEEE 802.3ab or 1000BASE-T.

1000BASE-X supports: Multimode fiber media Single-mode fiber media and A short-reach, 25-meter Copper media jumper.

Because most of the cabling installed inside buildings today is Category 5 copper, the IEEE 802.3 1000BASE-T standard supports GbE operation over the Category 5 cabling systems installed according to the specifications of ANSI/TIA/EIA-568A (1992, revision A in 1995).

I will let you read the Cisco web page, Figure 7 answers your question

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Reply to
gb

I read the Cisco page (mostly marketing spin) and found the following sentence that answered my question:

"1000 Mbps data rates are achieved by sending and receiving a 250 Mbps data stream over each of the four pairs simultaneously (4 X 250 Mbps = 1 Gbps)."

This implies that the 4 twisted pairs are simultaneously both sending and receiving separate 250Mbps data streams giving the 1000Mbps throughput in both directions. The picture showing hybrids in each twisted pair reinforces that each wire pair is indeed full duplex and provides additional detail on the physical link rates. This is what I take away from this, but if I have misunderstood, please correct me.

On your preference for optical fiber or even coaxial copper cable, yes, Fiber does seem to be better for many applications since it provides separate send and receive paths making it more immune to noise and increasing the allowable distance, especially for Single Mode Fiber (SMF). But, this comes at a high price since the cost of optical GbE interfaces, especially SMF are much more than for the copper RJ45.

RJ45 GbE seems to be the best way to interconnect network elements that are in close physical proximity (i.e. the same data cabinet) since it can be done very cheaply. As the article also explained, it is also a good way to increase bandwidth to end users when Cat5 already exists in a facility's wiring closets to desktops.

This was a very good thread. Thanks for correcting the initial reply and providing these links.

Bob

4

each

full

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Reply to
Bob Shuman

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