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802.3af Specifications CAT 3 CAT 5?


Hi all,

Can anyone shed some really light?

I have seen conflicting information on whether or not 802.3af supports CAT3. The specifications dont "seem" to suugest.

It is probably of course that 802.1q is out of the question, however 802.1p would make sense (and would be acceptable).

What about 10base2? (just kidding)

Anyone know? Definitive link?

4 Replies 4


You can try to use the CAT3 cable, really the only difference between CAT3 and CAT5 is the amount of twists in it. Try it out if you have to but you will probably only get a 10M connection at best. Your better off installing new cable.

Yes the customer has already tried more than 10Mb and it doesnt work (as suspected really).

Problem is that it covers around 1000 phone points and is too risky for me to even suggest "try it, see if it works", hence why I wanted to try and find out whether the spec said ok at 10Mb CAT3 as long as sub 100mtrs. Otherwise this part of my project is going to be VG248's!

802.3af will support Cat3. However, most of the phones are only cisco power, not 802.3af. We did a Cat3 install (historical building, couldn't run new cable) and locked all ports to 10Mb with local power cubes. Not ideal, but worked solid.

Hi, thanks for the reply, although kind of didnt update the notes as it was a little while ago. I had of our engineers do some local tests on 3750 switches running at 10mb with 802.1q and seemed to be fine. I have seen some more information that Cat3 par say will support 10mb. I will update the group on the results of further tests.

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