81 lines
3.3 KiB
HTML
81 lines
3.3 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<HEAD>
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<META NAME="GENERATOR" CONTENT="SGML-Tools 1.0.9">
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<TITLE>Linux Ethernet-Howto: Cables, Coax, Twisted Pair</TITLE>
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<LINK HREF="Ethernet-HOWTO-6.html" REL=next>
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<LINK HREF="Ethernet-HOWTO-4.html" REL=previous>
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<LINK HREF="Ethernet-HOWTO.html#toc5" REL=contents>
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</HEAD>
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<BODY>
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<A HREF="Ethernet-HOWTO-6.html">Next</A>
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<A HREF="Ethernet-HOWTO-4.html">Previous</A>
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<A HREF="Ethernet-HOWTO.html#toc5">Contents</A>
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<HR>
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<H2><A NAME="cable"></A> <A NAME="s5">5. Cables, Coax, Twisted Pair</A></H2>
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<P>If you are starting a network from scratch, you will probably
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be using Cat5 wire for 10/100baseT (twisted pair telco-style cables
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with RJ-45 eight wire `phone' connectors). If you stumble across
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some old surplus 10Base2 thin ethernet (RG58 co-ax cable with BNC
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connectors) it might be suitable for linking a few machines
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together in a home ethernet.
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The old-fashioned thick ethernet, RG5 or RG8 cable with N connectors
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is really obsolete and rarely seen anymore.
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<P>See
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<A HREF="Ethernet-HOWTO-1.html#cable-intro">Type of cable...</A> for
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an introductory look at cables.
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Also note that the FAQ from <EM>comp.dcom.lans.ethernet</EM> has a lot
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of useful information on cables and such. FTP to
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rtfm.mit.edu and look in <CODE>/pub/usenet-by-hierarchy/</CODE>
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for the FAQ for that newsgroup.
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<P>
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<H2><A NAME="bnc"></A> <A NAME="ss5.1">5.1 Thin Ethernet (thinnet)</A>
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</H2>
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<P>
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<P>
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<P>Thinnet (10Base-2) is pretty much obsolete now. It is fine for
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somebody playing around with a home network and old ISA cards.
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There are two main drawbacks to using thinnet. The first is that it
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is limited to 10Mb/sec - 100Mb/sec requires twisted pair. The second
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drawback is that if you have
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a big loop of machines connected together, and some bonehead breaks
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the loop by taking one cable off the side of his tee, the whole
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network goes down because it sees an infinite impedance (open
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circuit) instead of the required 50 ohm termination. Note that
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you can remove the tee piece from the card itself without killing
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the whole subnet, as long as you don't remove the cables from the
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tee itself. And if you are doing a small
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network of two machines, you <EM>still</EM> need the tees and the 50 ohm
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terminators -- you <EM>can't</EM> just cable them together!
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It is also vital that your cable have no `stubs' -- the `T'
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connectors must be attached directly to the ethercards.
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<P>
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<P>
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<H2><A NAME="utp"></A> <A NAME="ss5.2">5.2 Twisted Pair</A>
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</H2>
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<P>
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<P>Twisted pair networks require active hubs,
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which start around $50. You can pretty much ignore
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claims that you can use your existing telephone
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wiring as it is a rare installation where that turns out to be the
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case.
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<P>On the other hand, all 100Mb/sec
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ethernet proposals use twisted pair, and most new business
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installations use twisted pair. The wiring should be listed
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as Category 5. Anything less than Cat 5 is useless.
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<P>If you are only connecting two machines, it is possible to avoid
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using a hub by purchasing or making a special cross-over or null
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cable. But note that some cards that try to sense autonegotiation
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and so on expect to be talking to a hub and not another card, and
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thus may not work in this configuration.
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<P>
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<HR>
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<A HREF="Ethernet-HOWTO-6.html">Next</A>
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<A HREF="Ethernet-HOWTO-4.html">Previous</A>
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<A HREF="Ethernet-HOWTO.html#toc5">Contents</A>
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</HTML>
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