Network switch question

In my work I have experienced that some NICs don't work with some
network switches and I can't figure out why. I am especially having
trouble with computers where the NICs are integrated in the chipset.

Today when I tried to connect two computers via a Dlink DES-1005D
switch, only 5% of the pings got thru. I changed to a 5 years old
10Mbit hub from 3Com and there was no problem.

Both computers had 10/100 network connection capability, one of the
computers was a laptop with built in NIC. When I tried using a third
computer the communication was ok regardless of which switch/hub I
used. I used CAT5 cables that are ok....

I'm puzzled!!! Please help!

Thanks
Fredrik

Fredrik <(E-Mail Removed)> wrote:

>In my work I have experienced that some NICs don't work with some
>network switches and I can't figure out why. I am especially having
>trouble with computers where the NICs are integrated in the chipset.
>
>Today when I tried to connect two computers via a Dlink DES-1005D
>switch, only 5% of the pings got thru. I changed to a 5 years old
>10Mbit hub from 3Com and there was no problem.
>
>Both computers had 10/100 network connection capability, one of the
>computers was a laptop with built in NIC. When I tried using a third
>computer the communication was ok regardless of which switch/hub I
>used. I used CAT5 cables that are ok....

Did you try to connect the two computers using a crossover cable?
Is the connection capable of 100Mbit/s ?
I noticed that those builtin ethernet adapters are mostly pennyware.
They say it is a 100Mbit/s NIC but those cheap onboard chips are
unable to sustain that speed for more than a few seconds or just a few
KByte before they drop down again.

regards
André

Fredrik <(E-Mail Removed)> wrote:

>On Tue, 26 Aug 2003 22:30:24 +0200, André Franke
><(E-Mail Removed)> wrote:

>>Did you try to connect the two computers using a crossover cable?
>>Is the connection capable of 100Mbit/s ?

>Yes, and it works, but I haven't monitored the speed. Speed is not my
>concern really, I would be glad if it worked at all when connected to
>different switches. When moving the laptop from one room to another at
>the company and plugging it into another switch it SHOULD work. It
>works with other computers...

I see. But the speed may be the problem.
I don't know for sure, but I guess your switch is autosensing the
speed and capable of full duplex. Now let's assume both of your NICs
are configured to work at 100Mbit/s full duplex mode or even worse to
autosense too.
The switch autosenses 100Mbit/s networkspeed and full duplex mode and
a few seconds later the cheap NIC is unable to sustain the 100 Mbit/s
any longer and drops down to 10Mbit/s.
The switch autosenses 10Mbit/s on one side and half duplex mode and
drops down the speed to that value too. Then the cheap NIC goes up
again to the configured values...
Since autosensing takes some moments, it will be the same effect as a
broken cable.
So try the following:
Set both NICs to 10 Mbit/s half duplex mode manually.

regards
André

On Thu, 28 Aug 2003 20:18:48 +0200, André Franke <(E-Mail Removed)> wrote:
> I don't know for sure, but I guess your switch is autosensing the
> speed and capable of full duplex. Now let's assume both of your NICs
> are configured to work at 100Mbit/s full duplex mode or even worse to
> autosense too.

That is the way they should be. But you do know what "autosense" is,
don't you? In reality with any current networking product it is
"negotiated" not "sensed." Neither side can negotiate to something
without the other knowing about it.

> The switch autosenses 100Mbit/s networkspeed and full duplex mode and
> a few seconds later the cheap NIC is unable to sustain the 100 Mbit/s
> any longer and drops down to 10Mbit/s.

I really don't think that likely. That would take a more expensive
nic than just a cheap one which simply dealt with the data or
dropped it. That is, after all, how they work.

Further, I don't recall seeing in the spec any ability to
renegotiate after the link is established. That _would_ break the
link. It would require breaking the link in order to do a new
negotiation. If the gear has lights to indicate speed, duplex
and/or link, this behavior should be obvious.

> The switch autosenses 10Mbit/s on one side and half duplex mode and
> drops down the speed to that value too. Then the cheap NIC goes up
> again to the configured values...

Why? The switch has to be part of the negotiation when it happens.

> Set both NICs to 10 Mbit/s half duplex mode manually.

That's good to isolate products which have a flaw in their
implementation of the 802 link negotiation.

sdb

--
| Sylvan Butler | Not speaking for Hewlett-Packard | sbutler-boi.hp.com |
| Watch out for my e-mail address. Thank UCE. >>>> change ^ to @ <<<< |
It may be better to live under robber barons than under omnipotent moral
busybodies. The robber baron's cruelty may sometimes sleep, his
cupidity may at some point be satiated; but those who torment us for our
own good will torment us without end, for they do so with the approval
of their consciences. -- C. S. Lewis

Sylvan Butler <Znospam+(E-Mail Removed) d>
wrote:


>That _would_ break the link.

That's what happened, isn't it?

>If the gear has lights to indicate speed, duplex
>and/or link, this behavior should be obvious.

Obviously it is not obvious for the user.

So where is your information on how to solve the problem?
If you are the big pro you claim to be, why don't you just tell what
to do instead of discussing simplified descriptions of what may be
going on and how to solve the problem?
Didn't you find something written in your documentation archive?
I provide hints, based on my expierience, knowing that they work.
I try to keep my explanations simple so anyone can understand it and
can succesfully set up a network.
You only state, I said this or that wrong, and it works somewhat
different from what I explained. It won't help you much if you know
exactly how things work, but you are unable to change that in a way it
will function.

regards
André

On Fri, 29 Aug 2003 13:00:12 +0200, André Franke <(E-Mail Removed)> wrote:
> So where is your information on how to solve the problem?

What problem? Fredrik was asking why sometimes things work together
and sometimes they don't. You talked about how they work, I added
more information correcting you where you were wrong.

Further, I confirmed your only suggestion about locking down as a
good way to isolate problems in link negotiation.

> You only state, I said this or that wrong, and it works somewhat
> different from what I explained. It won't help you much if you know
> exactly how things work,

But that was the question Fredrik asked and which you answered.
Further, not enough info was provided to do more than guess.

Want more troubleshooting tips? If so, you should have asked. Of
course, you might be told to quit asking FAQs. Here's some tips you
can find on just about any google search of networking groups or on
networking basic info sites:

What do the link lights indicate? If they indicate a problem, what
problem? Does that change when you lock down to a specific rate (10
or 100) or duplex (half or full) on one end? What about the other
end? What about both ends? If locking to a specific rate and
duplex makes it work, then you know that negotiation implementation
is broken by one or both vendors. Often a driver or firmware update
can fix this.

Did you use the exact same cables for each test? If not, the cables
are suspect.

What happens if you wiggle the wires at the crimped on connections?
Wiggle back and forth and push in and pull out on the wire. If the
connection goes flaky, your cables are bad.

Is your cable plant sure to meet cat-5 specifications in all wiring
and terminations? If not, you are finding out why it is good to
meet specifications -- if you don't, sometimes things work,
sometimes they don't.

sdb
--
| Sylvan Butler | Not speaking for Hewlett-Packard | sbutler-boi.hp.com |
| Watch out for my e-mail address. Thank UCE. >>>> change ^ to @ <<<< |
It may be better to live under robber barons than under omnipotent moral
busybodies. The robber baron's cruelty may sometimes sleep, his
cupidity may at some point be satiated; but those who torment us for our
own good will torment us without end, for they do so with the approval
of their consciences. -- C. S. Lewis