Cat 5 upgrade to Cat 5e or Cat 6?


In the past month, I have spoken to two people who had been using very old routers (two diffferent brands) with a Cat 5 cable connecting a PC to the router and a Cat 5 cable connecting the router to a dsl or cable modem. When they tried to switch to a Cat 5e (in one case, he switched to a Cat 6) they could not get a connection. Is it possible that the very old router cannot handle Cat 5e or Cat 6? I thought that the newer cables were backward compatible? Appreciate hearing the experts' opinions. Thanks.


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In article , johnr999 writes

Newer cabling just tightens up the specs. (in effect, in this case). A 'better' grade of cable should just work.. My guess is one of the 'old' cables was a crossover, and the newer cables were straight through. - Older kit will probably not auto-detect the cable type, and so not work with the wrong type (wire-map) of cable. Philip Partridge

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Phil Partridge

DSL modems uses a crossover cable, not a standard straight through ethernet cable.

Most likly they didn't realize the cable they were using to connect their modem to a router was NOT a standard "straight through" ethernet cable at all, but actually a crossover cable.

Have them look real close and they will see its wired as a EIA/TIA 568A at one end and a EIA/TIA 568B at the other end.

Crossover Straight Through Pin 568A 568B 568A 568B

1 w/g w/o w/g w/g w/o w/o 2 g/w w/0 g/w g/w o/w o/w 3 w/o w/g w/o w/o w/g w/g 4 bl/w bl/b bl/w bl/w bl/b bl/b 5 w/bl w/bl w/bl w/bl w/bl w/bl 6 o/w g/w o/w o/w g/w g/w 7 w/br w/br w/br w/br w/br w/br 8 br/w br/w br/w br/w br/w br/w
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By the way, thanks to all for your responses. They have been really helpful.

Just to confirm: all DSL modems require a Crossover cable while all cable modems require a straight-through patch cable?


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Was that a logical statement?

It didn't look like one.

The manufacturer has instructions. A Fujitsu DSL modem from 5 years ago requires a crossover cable if you're going to one machine. A Westell DSL modem doesn't care since it is autosense.

I plug my Toshiba cable modem into a router and switch. I don't know what cable it needs, because the router is autosense. I was really happy to unload that Sharkfin unit a couple of years ago :-J

Carry a little 5 port switch with you and you won't ever need to guess. I got mine for about $30 at Wal-Mart. Or get yourself a couple of ethernet cables one straight through and one crossover.

Carl Navarro

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