Linux - NewbieThis Linux forum is for members that are new to Linux.
Just starting out and have a question?
If it is not in the man pages or the how-to's this is the place!
Welcome to LinuxQuestions.org, a friendly and active Linux Community.
You are currently viewing LQ as a guest. By joining our community you will have the ability to post topics, receive our newsletter, use the advanced search, subscribe to threads and access many other special features. Registration is quick, simple and absolutely free. Join our community today!
Note that registered members see fewer ads, and ContentLink is completely disabled once you log in.
If you have any problems with the registration process or your account login, please contact us. If you need to reset your password, click here.
Having a problem logging in? Please visit this page to clear all LQ-related cookies.
Introduction to Linux - A Hands on Guide
This guide was created as an overview of the Linux Operating System, geared toward new users as an exploration tour and getting started guide, with exercises at the end of each chapter.
For more advanced trainees it can be a desktop reference, and a collection of the base knowledge needed to proceed with system and network administration. This book contains many real life examples derived from the author's experience as a Linux system and network administrator, trainer and consultant. They hope these examples will help you to get a better understanding of the Linux system and that you feel encouraged to try out things on your own.
Click Here to receive this Complete Guide absolutely free.
i know this isnt directly related to this thread, but the search function brought me here, and it seems you have the knoledge....
anyways... i have questions on network cable.
1) how do you tell the difference between Twised, and untwisted net-cable.
2) is twised the stuff you use for direct NIC -> NIC or is it the other way around ?
3) is the cable from my NIC to broadband modem twisted or untwised ?
4) why ? why do you need different network cable depending on wether or not a hub is in your way ? and why not just have an adapter that goes on the end rather than making my old cable obsolite when i buy a 3rd pc + router. ?
The difference between a crossover cable and a straight through (regular) network cable is minute, but an extremely important difference.
Crossover cables have been phased out over the last few yesrs, and many circumstances where a crossover cable used to be needed can now be accomplished with a straight through cable along with the use of the now evercommon uplink port on switches, hubs, and the cheaper routers. By cheaper, I mean the ones for home or small network use, not the big cisco and other industrial size/strenght machines.
The way to tell a crossover from a straight through is to look at the colors of the 8 wires within the cable. Looking down on the end of the cable that has the pin side facing up at you, you'll see this color scheme left to right:
1) brown 2) brown/white 3)green 4) white/blue 5) blue 6) green/white 7) orange 8) orange white.
They actually get numbered the opposite way, right to left, but that is unimportant for our purposes here. If both ends of the cable have that scheme, you have the standard straight through cable that passes from computer to hub/switch/router.
This is the ordering for a crossover cable:
1) brown 2) brown/white 3) orange 4) blue/white 5)blue 6) orange/white 7) green 8) green/white.
Very important to note that this will be the color scheme on only ONE end of a crossover cable. The other end should be normal. The only cables of importance are the orange and greens - the blues and browns are useless the vast majority of the time, they just fill space.
To qwijibow: I assume by twisted you mean crossover, I'll operate under that premise, as I have never heard the term "twisted cable".
your question 1 was answered above
question 2) a crossover is what you would use to go directly from one NIC to another with no hub/switch/router between.
questions 3) Could be either, but most of the time a broadband modem will have a built in adapter that you spoke of, so a regular cable can be used where a crossover used to be needed. Plugging a crossover into your cable modem that was designed for a regular cable will not work, as it will effectively be double crossed, leaving you back at a regular position.
question 4) The crossover has become fairly phased out. You can still buy them and many systems use them, but going forward you'll see only regular cables in most if not all new installations. By twisting the pins on the receive (female) that the cable plugs into, you can make a crossover from a regular. The large problem with the crossover was that it couldn't scale. You could and still can go directly between machines with a crossover, but if you want to connect a 3rd machine, you're SOL because all the NIC interfaces have been used, unless you put 2 cards in one machine. The cost of a 6 foot cable is probably under $10 if you look around. You can get cables super cheap online ($2 for a cable is quite common, even in super small quantities). If you are setting up your home network for the first time, get a small (4 or 8 port hub, depending on the number of machines) and run only regular cables. If the hub has an uplink port, you'd plug your cable modem or dsl into that, and you can rock and roll. You may need to go up to the cheap home router if you want something doing DHCP, but you can get around that.
My home network:
cable modem runs directly into my main box, which has 2 NICs. The modem comes in and that card gets DHCP from my cable company. I them put local statics on my other card (220.127.116.11) and then each machine in my apartment has a static address (192.168.0.2-6), all configured with 192.168.0.1 as the gateway, also as the DNS server along with my ISP's s primary DNS server. The cable company can't cause problems, becasue by running it into a computer and not a router (ok my machine is functioning as a router, but it isn't one). I got an 8 port hub onlne for $8 dollars delivered, and built the cables myself. Even if I bought the cables, the six of them could have been had for less than $50.
If you are comfortable playing with wires, you could cut off the head of the crossover cable, and put a new head on it with the regular color order, thereby recycling the cable. The tool to crimp the head on will be about $30, so for just one cable it is cheaper to simply buy what you need.
Originally posted by qwijibow how do you tell the difference between Twised, and untwisted net-cable.
untwisted refers to cables like, for example, telephone cable... it's just straight without any twists...
remember, twists do not affect the order of the wires in the cable...
what differentiates a crossover cable from a regular cable is the _order_ of the wires...
is twised the stuff you use for direct NIC -> NIC or is it the other way around ?
both a straight through and crossover cable are usually twisted... if you look closely at any regular utp cable, you'll see that the 4 pairs of copper wires inside are uniformally twisted... this is done to reduce noise, interference... "crossover" refers to the order of the 4 pairs, not the twisted state...
is the cable from my NIC to broadband modem twisted or untwised ?
it's probably a regular straight-through UTP cable... broadband modems usually don't require a crossover cable... crossover cable is more for NIC-to-NIC wiring and the likes...
UTP means "Unshielded Twisted Pair"... that means if you cut through the outer plastic-like insulation to look inside the cable, you'll see the twisted wires right away, you won't need to go through a layer of additional "shield", the twist is the only noise insulation you get... with STP cables, you get that familiar metallic mesh surrounding the twists, providing additional insulation...
from some page i googled:
UTP or unshielded twisted pair cable is used on Ethernet 10BaseT and can also be used with Token Ring. It uses the RJ line of connectors (RJ45, RJ11, etc..)
STP or shielded twisted pair is used with the traditional Token Ring cabling or ICS - IBM Cabling System. It requires a custom connector. IBM STP (shielded twisted pair) has a characteristic impedance of 150 ohms.
Thank you so much for all that info. That is exactly what I wanted to know.
On a side note. Hearing all of this stuff and all these terms being thrown around for the first time seems to make this whole Linux affair seem a daunting task.
I've abused windoze for 10 years now and never learned about any of this stuff. I just assumed my expensive OS took care of it (or not).
But daunting as it may seem, I think it's important to learn this stuff so that I know what the heck is going on inside of this box in front of me. I'm not just a leech on it and throw up my hands when it doesn't work right.
But I could definitely see where one would venture into the wide world of *nix and quickly get overwhelmed and lost. The fact there are folks like you out there amazes me. I write a goofy noobie question that I could have typed in the search box and you send back a fantastic response. (I'll use the search box in the future so as not to abuse the privilege).
No problem man, it is not often that a question comes up that I feel confident to answer, but one about wiring I was ready for, as I often have to make cables for my company at work.
The search and google idea is very good. I've only been playing in linux for about 6 or so months, but I've learned a TON of things from this site, and also another good one is linuxcommand.org If you can't find a good answer on the search here, then I go to google, and also the specialized google.com/linux. If my search comes up nil, then I post here, and somebody usually writes back quickly.
Also jusy FYI, what I wrote is 100% OS independent. That will apply to windows boxes, Macs, all the subvarieties of linux/unix etc. The only time it would change would be if you were connecting with Token ring, or some of the other network technologies that have by and large fallen by the wayside.