On Saturday 15 Nov 2003 4:22 pm, Anguo wrote: > Right now, I am trying to figure out what kind of cables and > hardware I have. > > The setup is temporary and the primary purpose is to > setup/upgrade my friend's computer via internet and > transfer some big files from my computer. It is also a > learning experience for a more permanent setup in the near > future. > > I have borrowed some hardware. I also struggle a bit with > the terminology. As always I'll put complementary > information on the wiki. > > I have a "D-Link Ethernet Broadband Router".
> > A router is only a small box, and its fonctions are limited > while a hub can be a whole computer serving as a dedicated > server, right? No. See below. > > I have two cables. A short one, over a meter in length and a > long one, 20+ meters. > > If I understand well, we have two kinds of cable (looking > both at the link above and your email): > > 1- special 'Twisted Pair Crossover' cable/ cross-over > ethernet lead > > 2- 'Cat 5' 'twisted pair' (UTP) cables / straight-through > lead > > Both use the same RJ45 connectors. > > I am not sure about the UTP and Cat 5 bit: both have that > written on them. Do that mean that they are not crossover > cables? No. UTP is "Unshielded Twisted Pair" ie there is no overall braided screen around it, and pairs of wires are twisted together. CAT5 is an international standard for network wiring. Don't worry about either of them. > Doing your test, this is what I notice: > > For the short cable, I see the same colored cables at the > two ends, but the order is not the same: > orange-blue-green-red vs green-blue-orange-red (actually > the same but the other way round and with some > transposition.) > > For the long cable, the order of the colors are the same at > both ends. I would agree with you: the short wire is a cross-over, the long one is straight-through. > For the sake of completeness, which part of the information > written on the cable is relevant? > > The short one reads: > E195773 (UL) CM 75oC EMC Cat 5E UTP 4 PAIR 24 AWG HYPER-PLUS > PS-NEXT VERIFIED TO ISO/IEC 11801 004283M > > The long one reads: > ENHANCED CABLE CAT.5E UTP TYPE CM 24AWG 75oC S.C.E. 114481 > CMG ETL VERIFIED EIA/TIA-568A SHYARO CHI None of it. It all refers to the type of cable, not how it's connected. > From all this, I don't know what conclusion to take. > > In the case of someone buying the stuff in a supply shop, > what exactly should be written on the box, for both types > of cables? Normal patch cables are straight-through. Cross-over cables should be clearly marked as such. > Hmmm... again, what's the difference between a hub and a > router (if any)? A hub is a very simple box that basically joins all the wires up together. (It's a bit more complex than that, of course.) So with four machines A,B,C and D on the network only one of them can talk at any one time. A switch is very similar to a hub, but allows simultaneous conversations to happen at the same time, so A can talk to B while C is talking to D. But you can still only have one machine on each port. Also called a "switched hub." A router is an altogether more complex device that understands the protocols and decides where they need to go. So if one port leads to another network then the router only sends traffic out of that port if it needs to go there. In your case the traffic between your two machines would stay in your network, but both machines could talk to the Internet. Many broad-band routers have built-in firewalls. (A firewall filters the traffic going through it and only permits traffic that meets certain criteria. A good initial set-up is to allow all outgoing traffic, and no incoming traffic. That will not be sufficient if you need to run a mail server etc., and it stops some instant messanger functionality, but it is fairly safe.) > Would my D-link box I mentionned qualify? Yes. > It stands to logic that beside the adsl cable that would > connect in the WAN slot of the router, I would need two > length of straight-through cables. Not necessarily. A lot of switches and routers these days have logic in them that can correct a crossed-over cable. Check the manual. If so then you can use the cables that you have. From a quick browse on the D-Link website... If your router is a D-Link 502G then it would be better to use the cross-over cable between the computers. It only has one ethernet port and one USB port. Although you can use both to access the Internet it doesn't say that the two machines can talk to each other. All other routers mentioned on that site have at least four ethernet ports. I have just checked the 604's manual and it doesn't say that it handles cross-over cables. You could just try it and see, or an ethernet patch cable is cheap. Since this is a quick hack, I would prefer to use the router if possible. Using the cross-over cable between the machines means that you have to configure your machine to pass-through traffic to your friends machine. Webmin might make that easy, but not as easy as just plugging it in and working, as the router solution should. You do need some way of sharing files between the machines of course, NFS if his is a Linux machine, Samba if it's Windows. Or run an FTP server on your machine. I'm no expert on those things, but I think webmin would be useful. -- Richard Urwin
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