I'm having a very strange problem.
With some "low-price" Ethernet cards, for example those shipped with chipsets like rtl8139, via VT6105, DLINK DL10028A and connecting them to 3Com switches like 24 ports 3C16471 (not-managed).
Those cards autonegotiate 100baseTX, link appear to be active, but there is no chance to get a successfull ping to any host. If I force media type down to 10baseT full or half duplex those cards works ok.
I tried with Debian, Fedora and even netBSD. And the problem seems to be the same.
If I use ethernet cards like 3Com 3C905 works ok, the problem doesn't occur (tested with Linux and BSD).
I also tried those "low-price" cards with a Cisco switch and in that case the problem didn't occur.

Does anybody have any idea if the problem could be related to any hardware (cards or switches 3Com) limitation? Or any other suggestion to test?


Thanks in advance,
Matías

If you set up card and switch port to AUTO, will they negotiate up to 100BaseT full duplex?

Exactly. With those "low-price" cards they auto-negotiates up to 100BaseT, but there's no ping responses. With 3Com or other on-board cards works ok with 100BaseT.
These 3Com Switches are not managed, so I can't play with ports.

Any collisions or errors on card interfaces?

If it works at slow speeds or Half-duplex, then there's nothing wrong with your network topology or addressing scheme. So .. .

Bad cables?

You need CAT 5 or better for 100BaseT.

100BaseT needs better cable quality than 10BaseT. Yes the cables look the same, but poor quality cable will not work properly with 100BaseT, and that's "just the way it is".

Try changing the cables (one at a time) for better ones.

Some (more expensive) NICs might be able to handle poor quality cable better than others.

I tried diferent cables, all cat 5 cables. But I'll try with cat 6 one as soon as I can.
Is possible that more expensive NICs could handle poor cables...

Tredegar,

You were right! I tried with cat 6 cable and those "low price" NICs worked ok with 100BaseT and 3Com switches.
May be those NICs can't handle 100BaseT when cat 5 wires aren't from the best quality.

Thanks for the tips. Regards,
Matías

So it seems that cheap NICs will not adjust to "poor quality" cables (although the cables always LOOK identical to me).

Pleased you have it working now.

Thanks for the follow-up post.