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500' wire run works...why?!

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Okay everyone, I'll start off with this first:

IT ACTUALLY WORKS!

I'm insanely curious as to why, since by all rights it shouldn't.

Here's the history:

Our bank HAD a T1 between two buildings monitored by our telco with each building routed through two ACC Danubes connected through V.35 GDC 552s.

That line constantly fell off (once to twice a week) causing us to cycle the equipment and literally shutdown the network for 5-10 minutes at a time.

I got REALLY sick of it.

So I had an idea: We've got a 500' 200-pair telephone cable (that we ran in '93 and OWN completely). Why not use that?!

HERE'S MY SOLUTION:

I bought two CISCO 1721s with IP/IPX support and 10baseT WAN modules and connected them to hubs and puncheddown Cat5e on each end. It worked....WHOA.

Here's a (very simple) diagram to help explain it.

CISCO 1721--HUB-{500' phone cable}-HUB--CISCO 1721

Why the heck does it actually work? The 802.3 specs say this shouldn't work! It was just an experiment born from complete frustration! What'd I do right?! :)

13 replies

by maxwell edison

Your technical solution is outside the realm of my expertise. However, your apparent ingenuity and determination is to be admired. Some might call it "thinking outside the box". Others would call it determined to find a solution to a problem.

Your "experiment born from complete frustration" was really an experiment born from complete determination to solve a problem. What did you do right, you ask? You were thinking outside the box. Way to go!

Make sure that those who should know do know - when bonuses are handed out.

Thinking outside the box:

Draw 9 points on a sheet of paper arranged in a 3x3 configuration, all spaced equally apart both horizontally and vertically. Now, put your pencil on any of the dots, and without taking your pencil off the sheet, connect all nine dots by drawing only four straight lines.

Hint: Think outside the box.

Maxwell

(Email me if you want the solution.)

by frankl27

Figured out your 9-points puzzle - I'm accepting your answer for that fun little time-waster alone (gonna try to drive people nuts at work with it)!! :)

by rawright

My guess, based on a similar past experience, is that the products you selected are way over-designed! That's a very common practice, and the main difference between no-name cheap products and high quality name brands. The spec lays out a set of minimums, but a smart designer exceeds those levels in the actual design to ensure compliance under worst case conditions.

For years I ran a network built on RS-232, which should have allowed 9600bps at 50'. But because of the sturdiness on the Digi C/Con design, we got away with 19,200bps at 300'! And, like your solution, much of our net used 24-pair telco cable. Good job!

by road-dog

You are probably experiencing some collisions and other network problems on this link that are stopped by the router ports.

Since your operation is at 10MBPS as opposed to 1.5, the performance is still far and away better than what the users areused to. You're a hero! This is a classic example of a term we used to use in the Marines...."if its stupid and it works, it aint stupid!"

Make sure that you are prepared to show the management and downtime cost savings at your next performance /compensation review!!!

by otl

DS1 rated @ 24 Gauge what is the Exterior gauge of your cable ? For a 5 Mile run we used 14 ga.

Answer # 1 thru 3 are correct partially. Also you are not using loaded pairs, which is what you seem to have had in the past . Drop outs, no long term testing, I prefer 60 minutes to defer problems later.

Seeems your cable was properly installed and of a heavy enough gauge to allow DS1 transmission capabilities.

by jblancke

This will work but it has possibly fallen outside the specs of ethernet. you may want to run a cable tester on this line to see if it certifies as ethernet and at what speed. This telephone cable is most likely in conduit and has less noise introduced then running it through the plenum. The hub are repeating this signal so do the test on the cable only. you will more than likly see that it will not certify even though it does work. with this length yuo may see problems as data traffic increases. I would be very intrested in the results. and this may also work with long haul eternet interface cards, cisco does sell these. look up the specs on the interface cards. hope this helps!!

Regards
James

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