Date: Thu, 6 Jul 2000 16:47:22 -0500 From: "Jason" <jsmethers@pdq.net> Cc: <freebsd-hardware@FreeBSD.ORG> Subject: Re: RJ45 Message-ID: <004b01bfe793$c4649c80$73ce1f40@pdq.net> References: <200007051804.OAA01164@larryboy.graphics.cornell.edu>
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> >... or you want fully standards compliant cables. The other pairs should > >also be properly connected so they may be terminated and reduce any > >potential cross talk. But anyone who designs and installs quality networks > >doesn't cut corners, right? > > You don't need to connect and terminate the other pairs if you're not > using them. And if you're not using them you don't need a 4-pair cable. > I've seen plenty of 2-pair cables that run BaseT ethernet just fine. > Are you expecting cross-talk on non-existant pairs? > > -Mitch Wrong and right. You don't need to terminate STP if you don't really feel like it either for it to work to some minimum degree. Standards committees like to leave some amount of slack in the standard for future expansion, not to mention that using a less commonly used standard connector to help prevent to accidental mix up. Of course, if you are using 2 pair cable, there are no other pairs for cross talk or antening of stray signals through the unterminated pair.. You may get by with no noticeable problems at all in 10Base Ethernet systems with 4 pair cable with the 2 unused pairs unterminated, but in 100Base Ethernet systems you will likely notice problems leaving the other 2 unused pairs unterminated. How much more trouble is it really to terminate the pairs if existent versus how much more trouble it can be to leave them unterminated? Some of the same concepts as unterminated STP. There tends to be reasons that standards are the way they are. - Jason To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hardware" in the body of the message
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