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View Full Version : Gigabit Ethernet - Same Cables?


Blue Velvet
Jul 4, 2004, 06:59 PM
With the imminent arrival of our 2.5ghz G5s at work, we're going to get rid of our T 10/100 switch and purchase a Gigabit switch for our 4-user network.

Do we need to replace the cables with something different or continue using the same ones?

Can't find anyone who can tell me def. one way or the other...

Any words of wisdom much appreciated!

Thanks in advance.

Horrortaxi
Jul 4, 2004, 07:08 PM
I think you need Cat 6.

crazzyeddie
Jul 4, 2004, 07:22 PM
Yep, you need CAT6.

Blue Velvet
Jul 4, 2004, 07:27 PM
OK, thanx for that -- any way of telling what the current ones are?
They were there before I started working there.

All I know is... they're green!

But seriously, much appreciated.

jsw
Jul 4, 2004, 08:00 PM
It's very, very likely they're not CAT 6. Try them. If you get gigabit speeds, you're golden.

Horrortaxi
Jul 4, 2004, 09:11 PM
It might say on the cable. Cat 6 is noticibly thicker than cat 5.

EminenceGrise
Jul 4, 2004, 10:36 PM
The cables you have should work fine as long as they are Cat5, unless they happen to particularly ancient. Gigabit Ethernet is designed to work over standard Cat5 (100MHz) cable, but of course works better with Cat5e (350MHz), or Cat6 (500MHz). Most recent Cat5 cable is Cat5e anyway, so you should be good to go with what you have as long as it's good quality semi-recent stuff. Most of the time, the cable rating is printed (along with the manufaturer and reel footage) on the cable jacket about every 1-2 feet; look for Cat5, Cat5e, or Cat6. Often, at least on the Cat5e stuff, it will also have '350MHz' or '350' printed next to (or instead of) the Cat5e bit. The only problem you might have is if one of normally unused pairs for 10/100BT is bad and has gone unnoticed - GigE needs all four pair (8 conductors) to work correctly (10/100BT only uses two pair) - this shouldn't be an issue with any recent cabling though, most good stuff has all 4 pair tested.

Cat6, IMHO, is overkill for your small 4 machine network. The only place you would likely need Cat6 is on a high volume server, e.g. one that would actually be able to push the max practical amount of traffic over a GigE link (about 800Mbit/s, roughly). 800Mbit/s is 100MB/s - you will have a hard time getting a G5 (well, 'stock', anyway) to sustain that kind of transfer rate, mainly because the disk drives (and system bus to a lesser extent) will have a hard time pushing that much data for extended periods of time. I haven't seen any hard numbers, but you're more likely to see 200-300Mbit/s tops from a G5; Cat5e can easily handle this without any issues (and probably plain old Cat5 too).

My advice is to use what you have now, and only upgrade it if you have problems getting the GigE kit to run at full speed. It's better to upgrade it later if necessary, then waste a bunch of cash up front on something you don't need. If you do have to get new cable, I'd say Cat5e would be fine, and is still a bit cheaper than the Cat6 stuff. Probably by the time you'd actually need Cat 6, you'd want fiber instead anyway. ;)

Blue Velvet
Jul 4, 2004, 11:26 PM
...My advice is to use what you have now, and only upgrade it if you have problems getting the GigE kit to run at full speed. It's better to upgrade it later if necessary, then waste a bunch of cash up front on something you don't need. If you do have to get new cable, I'd say Cat5e would be fine, and is still a bit cheaper than the Cat6 stuff. Probably by the time you'd actually need Cat 6, you'd want fiber instead anyway. ;)


Thanks for that, your eminence! Really helped to clear things up. It's actually an eight machine network with 4 x dedicated G4s doing tasks like small server, colour RIP, PDF creating, ISDN etc.

Still, can never have enough speed!