SUMMARY: back-to-back with FastEthernet

From: Luca Pizzinato (
Date: Wed Sep 24 1997 - 03:52:53 CDT

Hi SMs.

The correct answer was: use a Cat5 cable (see the original question below)

I was using the old crossed cable that I prepared myself.

Anyway, even if the link is running fine now, it seems that the same ftp session that at 10Mbit/s had a throughput of 290Kbit/s now runs at 500Kbit/s. I expected at least 2 or 3MB/s.
One of you, Tomasz M. Wolniewicz, says that he has a similar configuration running at 5MB/s.

I will post another question to the list as soon as I have a precise benchmark.

Thanks to:

Jon Bidinger <>
Tim Carlson <>
Birger A. Wathne <birger@Vest.Sdata.No>
Sean McInerney <>
Benjamin Cline <>
Russ Poffenberger <>
Mark -
Russell David <>
Vipin Gupta <>
Tomasz Wolniewicz <>
Aggelos P. Varvitsiotis <>

The question:

Hi All.

Does anybody have experience with back-to-back TP network using 100Mbit/s interfaces?
It seems to me that this kind of connection can work only at 10Mbit/s.

I have here 2 machines that till yesterday were connected back-to-back through their 10Mbit/s Eth. interface. Never had problems.

Yesterday I mounted a FastEthernet SBus card on each of them.
Well, I can telnet from one to each other, but the link is really unstable. When I run a command like "ls -lR" during a telnet session, the output scrolls, then it hangs for several seconds, then it continues, etc.
I tried to run "ping -s <dest> 1400 100", and I had only 68% packets received !

Then I tryed to replace the TP crossed-cable with 2 normal TP cables + hub 10Mbit/s: everything works fine, but of course at 10Mbit/s.

Any suggestion?

Luca Pizzinato


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