Can get 10mbit/s but not 100mbit/s

I have 2 PC's on a LAN. One of them is a midi tower case a Realtek 8139, the
other is a micro-ATX with an onboard NVidia networking controller. I can
connect both PCs at 10mbit/s half duplex just fine but I cannot connect them
properly at 100mbit/s half duplex. I have even searched
PracticallyNetworked.com and found nothing that relates to this problem.

With the main PC using the Realtek 8139 we had an older PC ages ago on the
other end, also using an 8139. This worked fine at 100mbit/s half duplex, so
this rules out any physical problem

At the moment it is on 10mbit/s half duplex but I want 100mbit/s. How can I
sort this out?

Sim

On Mon, 17 Oct 2005 17:11:00 GMT, "Sim" <(E-Mail Removed)>
wrote:
>
>With the main PC using the Realtek 8139 we had an older PC ages ago on the
>other end, also using an 8139. This worked fine at 100mbit/s half duplex, so
>this rules out any physical problem

I'm not sure if you can that that ;-)
>
>At the moment it is on 10mbit/s half duplex but I want 100mbit/s. How can I
>sort this out?

How are the cables wired up (were they bought or home made etc)?

Your symptoms are typical of when the TX and RX pairs have been messed
up?

From memory, the main pins should be .. (holding the plug with the
cable hanging down and the contacts facing you, left to right ..)

1 = TX+
2 = TX-
3 = RX+

and

6 = RX-

You should be able to see the colours through the plug and you need to
check that the 'pairs' (ie blue and white / blue) are on pins 1+2 and
3+6.

A badly made cable will probably work ok at 10M (that will run over
damp string) but won't support 100M (or 1G!).

All the best ..

T i m

"T i m" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> On Mon, 17 Oct 2005 17:11:00 GMT, "Sim" <(E-Mail Removed)>
> wrote:
>>
>>With the main PC using the Realtek 8139 we had an older PC ages ago on the
>>other end, also using an 8139. This worked fine at 100mbit/s half duplex,
>>so
>>this rules out any physical problem
>
> I'm not sure if you can that that ;-)
>>
>>At the moment it is on 10mbit/s half duplex but I want 100mbit/s. How can
>>I
>>sort this out?
>
> How are the cables wired up (were they bought or home made etc)?

If I use both PCs fitted with Realtek 8139s it supports 100Mbps without any
problem. The cables are fine. In my opinion I think its a compatibility
issue.

In message <4gW4f.1359$(E-Mail Removed)>, Sim
<(E-Mail Removed)> writes
>If I use both PCs fitted with Realtek 8139s it supports 100Mbps without any
>problem. The cables are fine. In my opinion I think its a compatibility
>issue.
>
>
I assume you have a crossover cable? What happens if you force the
Nvidia to 100Mbps?
--
Clint Sharp

On Mon, 17 Oct 2005 23:15:12 GMT, "Sim" <(E-Mail Removed)>
wrote:


>> How are the cables wired up (were they bought or home made etc)?
>
>If I use both PCs fitted with Realtek 8139s it supports 100Mbps without any
>problem. The cables are fine. In my opinion I think its a compatibility
>issue.
>
You could be right .. but how do you know the 'cables are fine' btw
(other that it appears to work with a particular make / model of
card)?

I'm not suggesting there is a problem with the cabling but I have
heard of / witnessed too many 'professional' (and sometimes big) flood
wiring installations where the cables have been incorrectly paired?
One such instance involved an engineer flying to France and spending
the weekend re-terminating 100 Cat5 cables (200 'ends') because they
had been made up wrong in the UK workshop. ;-(

Just recemtly I noticed my mate had a 10M hub at one end of a link and
a 100M at the other of his small Unit. All the PC's had 100M cards.

I checked the interconnecting cable and it was Cat5 so good for 100M
so got him a 100M switch for that end.

All seemed ok for a while (couple of hours) then he rang me to say it
had all stopped workiing .. or more correctly had 'all gone weird'.

I popped back and inspected the pinout of the RJ45 plugs and they were
wired up incorrectly (pin 1-2 one pair, pin 3-4 another etc).
Suspecting this might be the case I had taken my crimping stuff,
fitted two new plugs and away it all went ;-)

Apparently it had run 'ok' for a couple of years .. at 10M that is ..
and was probably why the 'professional company' that installed it all
ended up putting a 10M hub at one end (as the only way they could make
it work ..) ?

All the best ..

T i m

"Clint Sharp" <(E-Mail Removed)> wrote in message
news:ykGdSkBw+(E-Mail Removed)...
> In message <4gW4f.1359$(E-Mail Removed)>, Sim
> <(E-Mail Removed)> writes
>>If I use both PCs fitted with Realtek 8139s it supports 100Mbps without
>>any
>>problem. The cables are fine. In my opinion I think its a compatibility
>>issue.
>>
>>
> I assume you have a crossover cable? What happens if you force the Nvidia
> to 100Mbps?

When I try to ping from the RTL8139 to the NVidia it recieves the first few
pings, then theres packet loss. There is always packet loss vice versa.

In message <qUz5f.8765$(E-Mail Removed)>, Sim
<(E-Mail Removed)> writes
>When I try to ping from the RTL8139 to the NVidia it recieves the first few
>pings, then theres packet loss. There is always packet loss vice versa.
>
>
Can you borrow a hub and a couple of known good patch cables to replace
the existing cable?


--
Clint Sharp

>I popped back and inspected the pinout of the RJ45 plugs and they were
>wired up incorrectly (pin 1-2 one pair, pin 3-4 another etc).
>Suspecting this might be the case I had taken my crimping stuff,
>fitted two new plugs and away it all went ;-)

This has shed light on a problem I have had repeatedly - network
cabling working at 10 Mb rather than 100. I presumed that so long as
the wiring was consistent in the RJ45 plugs at both ends of a cable
all was OK. Two questions please:
1. Why does it matter which wires are used?
2. What is the correct order of colours (wire hanging down, pins
facing me)?
Thanks

On Thu, 20 Oct 2005 08:15:42 GMT, James Ikom <(E-Mail Removed)>
wrote:

>1. Why does it matter which wires are used?

pairs are twisted and should have the same thing in the same pair eg
transmit in one twisted pair, receive in another.

>2. What is the correct order of colours (wire hanging down, pins
>facing me)?

http://www.alatec.com/info/rj45.html
http://yoda.uvi.edu/InfoTech/rj45.htm

Phil
--

Usenet spam eaten by a Hamster http://www.tglsoft.de/
No more cable clowns :-))
Please do not feed or re-quote the trolls.

Many thanks Phil


On Thu, 20 Oct 2005 09:45:02 +0100, Phil Thompson
<(E-Mail Removed)> wrote:

>On Thu, 20 Oct 2005 08:15:42 GMT, James Ikom <(E-Mail Removed)>
>wrote:
>
>>1. Why does it matter which wires are used?
>
>pairs are twisted and should have the same thing in the same pair eg
>transmit in one twisted pair, receive in another.
>
>>2. What is the correct order of colours (wire hanging down, pins
>>facing me)?
>
>http://www.alatec.com/info/rj45.html
>http://yoda.uvi.edu/InfoTech/rj45.htm
>
>Phil