INTELLIGENT WORK FORUMS
FOR COMPUTER PROFESSIONALS
FIRST NAME
*
LAST NAME
*
*
MESSAGE
*
ADDITIONAL DETAILS
Thanks. We have received your request and will respond promptly.
Log In
Are you a
Computer / IT professional?
Join Tek-Tips Forums!
*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.
Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Tek-Tips Posting Policies
100Mbps Using CAT3 on short distances?
3
thread575-1481462 Forum Search FAQs Links MVPsForum
Search
FAQs
Links
MVPs
(ISP)
(OP)
18 Jun 08 22:25Can a regular fast Ethernet switch use CAT3 wiring instead of CAT5 wiring to transmit 100Mbps over short distances? CAT3 is usually used in telephone networks, and I know it can support 10Base-T at 10Mbps. 100Base-T aka Fast Ethernet is supposed to have CAT5 at minimum. What happens if CAT3 is used? I know it is not recommended, but will it work, or will the switch auto fall back to 10Mbps?
(TechnicalUser)
18 Jun 08 22:26try it
(ISP)
(OP)
18 Jun 08 22:30Hello,
I would try it, but I have the necessay equipment to do so. Would anyone be willing to try this for me?
2
wires(TechnicalUser)
18 Jun 08 23:34Some of the older runs I work with are cat3 and they run 100Base-T just fine. The longest run is around 150'.
This is not an endorsement of this practice but in all the cases I have tried it worked fine. Did have to re-terminate one or two due to shoddy workmanship.
In NO case should you install cat3 as a cost saving measure.
Your Mileage May Vary
(ISP)
(OP)
18 Jun 08 23:40wires,
This is EXACTLY what I wanted to know. Do you have any recommendations or advice? I would love to use CAT5, but the CAT3 wire is the only real option. It would cost quite a bit of money to run new wire due to brick walls.
Were you able to actually transmit 100Mbps?
(TechnicalUser)
19 Jun 08 03:27A managed switch would be good so you can keep an eye on error counts. You can get a Dell 3024 switch for under $75 on eBay. With software version 6.1.2.3291 you get statistics, counter summary, errors received which will tell you real fast how your wiring is performing.
As I said before I get 100M but the terminations HAVE to be correct. Twists have to be maintained and the cables cannot be damaged. A bunch of old telephone wiring on 66 blocks will likely need rework.
If you have the choice rewire. Don't try to be a penny pinching hero and have the whole enterprise go down in flames. If this is a new place you are moving into think about how difficult it will be to rewire once everything is moved in and everyone is ready to work. Test BEFORE use.
Good luck.
(TechnicalUser)
19 Jun 08 08:28Make sure your wiring is actually CAT3 and not just older beige jacketed station wiring that was installed long before the Telcos cared about packetized digital transmission or whether you have 7, 11 or 17 twists per inch.(31 year telco veteran)
NCSS NCTS NCTE
(Programmer)
19 Jun 08 10:20 http://ethernetextender.com/ethernet%20extenders/860.phpmay be cheaper than re-wiring. If you have a whole building, http://ethernetextender.com/point-to-multipoint.php
I tried to remain child-like, all I acheived was childish.
(Vendor)
19 Jun 08 11:35I can see using a CAT3 cable or an extender for a one off situation that you have no choice, but for a whole company?
What happens when half of it works and half of it doesn't?
Or it is inconistent? Unreliable?
Who do you blame then? My take on this is if you cannot afford to do it right don't do it at all. Just put a phone one everyone's desk and say "we like to pretend this is 1984", we don't need a network.
As a network engineer I would not install a customer network running on CAT3. I would walk away and save the headache for someone else who likes them.
My 2 cents on this subject.
(ISP)
(OP)
19 Jun 08 13:09I am aware of the VDSL solutions that enable 100Mbps over CAT3, but I am trying to avoid that solution. VDSL is still very expensive.
This is for a townhome compex. There are 20 building each with 7 houses. At the end of each building the seven CAT3 cables terminate. I plan to run fiber to each building, and then was hoping I could service each house house using the CAT3 cables.
I know AT&T uverse does the with VDSL, but those runs are usually much longer (0-1500 FT). From one end of the building to the other is max 150 FT, and each run gets 20 FT shorter from there. All of this CAT3 wire is new, we are not talking about 30 year old CAT3 cable here. I would love to run newer CAT5e cable, but I believe install cost would be to high and would require premession from every townhome owner to gain access to their attic.
(TechnicalUser)
19 Jun 08 14:59VDSL, ADSL, ETHERNET are all different and have different transmission requirements and bandwidths. The CATEGORY rating refers to the ETHERNET transmission protocol. So you can't compare one to the other, apples and oranges!! There are a variety of factors that come into play when you try to apply a set of specifications from one class to another class.
In regards to trying to use 100BaseT on CAT3 cable, it may work for a while but you may end up with a lot of problems:
excessive crosstalk, dropped packets, excessive resends, interference, etc. With those types of conditions it will take longer to send data or files, cause more bottle necks, to get it right, and end up with unhappy customers.
....JIM....
(Programmer)
19 Jun 08 16:47Cat 3 is going to work fine for 10 meg ethernet. (it will even do full duplex) 100 meg fiber to each townhouse and seven 10 meg clients by 20 buildings is 1.4 gig total bandwidth. That is a LOT of bandwidth to provide.
I tried to remain child-like, all I acheived was childish.
(MIS)
20 Jun 08 10:47The fact is that you can run 100 Mbit over the Cat-3. It is not a good idea, but you can do it. I agree with the suggestion to have a managed switch so you can keep track of the errors, because there will be errors.
My suggestion for you if you proceed with the connections as you have laid out is to clearly document what you have done, and how it deviates form all recommended practices. I would make sure who ever is managing the end user/customers understands there could be performance issues at the end user level. As long as all parties involved are aware of, and understand the implications of wiring the system this way and agree to the level of performance then you are covered. It is not a matter of whether you will receive interference and errors on the network, it is a matter of how much, and how much your end users are willing to accept.
(IS/IT--Management)
24 Jun 08 05:38A lot of big companies I have worked in recently are limiting all their ports to 10 Mbits again now anyway to increase the overall speed and consistancy for all users. Ever larger files being constantly copied back and forth all over the place are causing speed issues for companies as a whole and putting everyone on 10 Mbits can drastically improve the situation at peak times (for everyone except those copying the 2gig files over the network of course!!)You may be better off using the cat3 but using it at 10Mbit.
Adrian Paris
Paris Engineering Ltd
http://www.ForumKB.com
Google search of just tech forums & articles
(very useful, honest!)
(MIS)
25 Jun 08 02:29The problem you're going to have is that once those CAT3 cables get into the unit, they are probably going to be daisy-chained throughout the unit.good luck with that
MCSE CCNA CCDA
(TechnicalUser)
26 Jun 08 19:11Like others have said -- walk away if possible.
I would definitely do the Cat5 upgrade.
A (relatively) big cost for now, but down the road alot of flexibility.
(Vendor)
30 Jun 08 14:27why are the brick walls a limiter for you? you will be replacing the existing cat 3 with a cat 5. Just use the cat 3 as your pull string for the cat 5, this should get you thru the brick without having to re-drill
----------------------------
'Rule 29', "The enemy of my enemy is my enemy's enemy. No more. No less."
----------------------------
JerryReeve
Communication Systems Int'l
com-sys.com
(MIS)
4 Jul 08 03:21In my business, I see this all the time, folks trying to retro-fit an MDU to provide internet, etc.Trust me on this, the money you think you're saving by using the existing CAT3 is going to be eaten up in support costs very quickly.
MCSE CCNA CCDA
(TechnicalUser)
4 Jul 08 20:46I would use CAT 3 for voice applications. For data, I would run with CAT 5E or CAT 6.
If it ain't broke, I haven't fixed it yet.
(Vendor)
8 Aug 08 20:06A couple of months ago I set up a phone line without a DSL signal on it so that 2 modems could be connected. One at either end so that one would act as a modem and the other would act as the server. The 2 units would communicate the same as you would on the internet. 2 network cards in the one CPU is supposed to allowed the other to access network and internet.
(Vendor)
9 Aug 08 09:37I started working for a LEC in 1998 and our office had Cat3 wiring terminating in 66 blocks and the other end of the cable had 2 RJ45 jacks. This way we got 2 network drops for each cable. At the time we had old 10 meg switches and it worked fine.In 2007 we upgraded to 100 MB switches. Guess what it still works fine. Our longest run was 200' in a drop ceiling and over flourescent light fixtures, conduits, etc. It is a myth that you have to use Cat5 for it to work. That is as long as you do not have RF or EMF interference causing inductance into your cable.Here is what I would do. Are these homeowners or rentals? I would install this as is and tell them that if there are problems then you would need the access to pull new cable and they would probably agree. You would probably have to work some odd hours to accomodate the owner.2nd is that if you have to pull cable, the best thing is to run a conduit to each so the next time you have to pull a cable you only need access to both ends.If this is a condo unit then there has to be some sort of access to all attics. What if the end unit needed some new electrical service run? What about under the buildings? Is there a crawl space?
Signature===========================================
Artificial Intelligence Is No Match for Natural Stupidity.
The latest survey shows that 3 out of 4 people make up 75% of the population.
The original point and click interface was a Smith & Wesson.
Red meat is not bad for you, it is the green fuzzy meat that is bad.
(TechnicalUser)
26 Aug 08 09:22I would not use "Cat 3". There is no substitute for peace of mind! "Cross-talk" is going to be a issue which affects performance,If you use "cat 3" at 100 mb or higher.Can you look a client in the eye and guarantee that person that they have have at least the minimal performance?I think not. what legal ramifications does skimping on wire have? Do you value your rep? How much are you going to save in the long run by using cat3? Prices are going up so 5 years from now when you have to do it again you will actually pay more. go ahead and bite the bullet and put in the best you can afford now or stay at 10mb and be happy.
people who say you can run it haven't had any formal training on network cabling please be cautious. get someone in with a good cable analyzer to test cat 3 at cat5 and above levels and see what happens.
(TechnicalUser)
4 Sep 08 10:29Upgrade to Cat5. It is going to work alot better, it is what they need, and it is a good job and an easy sale for you. What's the problem?
(Programmer)
8 Sep 08 00:01There once existed something called 100BASE-T4. As suggested by the name, four twisted pairs (all eight wires) were used to produce a "fast ethernet" link over CAT3. I doubt any of the new switches support this old method of Ethernet signalling/negotiation, which involved the use of QAM. I'm sure that new NICs don't either. I mean, you'd have to find some old ISA bus stuff that no one makes or supports anymore.Anyway, my point is that you weren't dreaming when you thought you once heard that CAT3 would support a 100Mbps Fast Ethernet connection. But it was never made a standard; instead CAT3 was demoted to support 16Mbps at 100Mhz.While it may appear that you "pulled it off" by getting a 100M link light on your switch, I would expect a quality tester to show a great deal of errors. You won't see the errors directly at the Application layer. Instead, it will manifest itself as random slowness and excessive chatter at the switch.Replace all horizontal wiring with 5e or better. It's the standard.
Tim Alberstein
www.dagwoodsystems.com
Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.
Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.
Click Here to join Tek-Tips and talk with other members! Already a Member? Login
For more information Cat3 Cable for Communication Networks, please get in touch with us!