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Maximum Segment Length for 10Base-T
klenze May-19-02 12:15 PM
First a lot of praise on your website Larry. You definitely have the ability to teach technical material and present it (both visually and in writing) so that it's easily understood. Great resource!

Now on to my Question 1:
On http://duxcw.com/digest/Howto/network/cable/cable7.htm you write: "The total length of wire segments between a PC and a hub or between two PC's cannot exceed 100 Meters (328 feet or about the length of a football field) for 100BASE-TX and 300 Meters for 10BASE-T". On each and every other resource I have visited it's said the maximum cable run for 10Base-T from transmitter to receiver is 100m (328 feet), and not 300m as you describe. On http://www.linksys.com/edu/cabling.asp , Linksys limits the maximum cable run for 10Base-T to 328 feet. I take your word as my definitive guide, but can you clarify? Could it be that EIA/TIA specs limits category cabling to 100m (328 feet), but in reality you tested it all out and found that 300m works just fine?

Question 2: Let's assume you are right about maximum network segment of a 10Base-T is 300m and we apply the loosely accurate "5-4-3 Rule", then would the maximum network diameter be about 1200m? (Remember this discussion refers to 10Base-T.)

Modem--10ft----Router---300m---Switch1--300m----Switch2--300m----Switch3---300m-----PC

Question 3: Is the Router counted as a Switch?

Question 4: The 5-4-3 Rule states that only 3 segments can be populated. Does that mean you can only attach PC's to 3 Switches? Could anyone elaborate why that is?

Question 5: Let's assume I would like to attach a PC to Switch 2 above. The cable run between switch and PC is 50feet. Would that be in violation of the maximum network diameter for 10Base-T using above topology? Doesn't the rule state that endpoint to endpoint has to be within 1200meters in my application of 10Base-T? From what I understand I'm in violation of 50feet.

Thanks for all your help and have a good Sunday! Stefan


1. RE: Maximum Segment Length for 10Base-T
trumpetr May-19-02 01:53 PM
In response to message 0
Stefan, I asked some of the same questions... I think that they show up on around page 4 or 5 of this forum it's Topic #1772 titled Network Segment Lengths.

That may help some.

MC


2. RE: Maximum Segment Length for 10Base-T
lbyard May-20-02 01:06 PM
In response to message 1
http://duxcw.com/digest/Howto/network/cable/cable7.htm was in error and has been corrected. The maximum segment length for 10BASE-T is the same as 100BASE-TX: 100 Meters (328 feet). Thank you. Sigh! I would guess that millions of people have read that page and it was written so long ago that I don’t remember where I got the number from.

What is the problem that you are trying to solve? Larry


3. RE: Maximum Segment Length for 10Base-T
klenze May-20-02 02:57 PM
In response to message 2
Thanks for your responses -Larry and MC. MC's original posting #1772 actually served as background material for my posting. What I'm trying to understand is the absolute cable length limitations using 10Base-T and 100Base -T before I have to make the jump to the more expensive use of fiber cabling.

To correct and reiterate my original posting:

Question 1: So the maximum network segment of a 10Base-T is 100m and we apply the loosely accurate "5-4-3 Rule", then would the maximum network diameter be about 400m?

Modem--10ft----Router---100m---Switch1--100m----Switch2--100m----Switch3---100m-----PC

Question 2: Is the Router counted as a Switch, or could I add a 4th Switch?

Question 3: The 5-4-3 Rule states that only 3 segments can be populated. Does that mean you can only attach PC's to 3 Switches? Could anyone elaborate why that is?

Question 4: Isn't there some kernel of truth that 10BASE-T still allows longer cable runs, but it would be "out of spec"? (Something that was earlier stated on your website and in topic #1789 where Larry responds: "The maximum for 10 MHz 10BASE-T is 185 meters."

My claim is simply based upon that Attenuation Loss is lower at the 10Mhz frequency 10BASE-T operates at. Has anyone tried to stretch the cable run limitations of 100m?

Question 5: Let's assume I would like to attach a PC to Switch 2 above. The cable run between switch and PC is 50m. Would that be in violation of the maximum network diameter for 10Base-T using above topology? Doesn't the rule state that endpoint to endpoint has to be within 400meters in my application of 10Base-T? From what I understand I'm in violation of 50m when connecting PC to switch 2, but then again the max cable length from switch to node is 100m. Which rule prevails?

Thanks again. Stefan


4. RE: Maximum Segment Length for 10Base-T
lbyard May-20-02 05:11 PM
In response to message 3
1. I don’t think I would attempt something like…

Modem--10ft----Router---100m---Switch1--100m----Switch2--100m----Switch3---100m-----PC

It just plain too complicated. To set the record straight… Most of the networks we’ve (Dux Computer Works) built were for small businesses. Except for one case, I do not we believe we have built a network with a diameter that was greater than 100 meters. The one I do recall was installed quite a few years ago and used 10BASE5 (thickwire coax) Ethernet to overcome distance limitations. The maximum length for a 10BASE5 network is 500 meters (hope I got that one right). Why are you limiting the MODEM leg to 10 feet?

2. Most routers are a combination of a NAT and a switch.

3. I’ll defer to Charles Spurgeon on that question, question 5, and the specifics of question 1. http://www.ethermanage.com/ethernet/100quickref/ch14qr_2.html#HEADING1.

>Question 4: Isn't there some kernel of truth that 10BASE-T still allows longer cable runs, but it would be "out of spec"? (Something that was earlier stated on your website and in topic #1789 where Larry responds: "The maximum for 10 MHz 10BASE-T is 185 meters."

A 10BASE2 (thinwire coax) segment has a maximum length of 185 Meters. As I understand it, 100BASE-TX is limited to 100 Meters because of timing factors (the time required for a frame to propagate down the cable, latency, and a Ethernet a collision signal to return) whereas 10 BASE-T is limited (the timing limitation may be 185 Meters, or maybe it is the 300 Meters I originally stated in error—I’ll let someone else work the math on it, if does not becomes a real-world need.) by the electrical limitations of the twisted-pair cable (probably the capacitance between the wires) and nominally to 100 Meters. I have read that it can be extended, perhaps, up to 150 meters, but I wouldn’t bet a network installation on it. I will say that what I have read on the subject is probably old and may predate CAT 5 and 5E cable.

You might find some useful info in http://duxcw.com/dcforum/DCForumID2/1748.html. Larry


6. RE: Maximum Segment Length for 10Base-T
klenze May-20-02 06:54 PM
In response to message 4
Thanks - topic closed on my end.
(My distance between modem-to-router of 10ft was just for the sake of argument)

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