RE: connecting two hosts with crossover cable and autonegotiation

From: Matt Zagrabelny
Date: Thu May 29 2008 - 09:59:16 EST


On Wed, 2008-05-28 at 16:02 -0700, Jeff Haran wrote:
> > -----Original Message-----
> > From: linux-net-owner@xxxxxxxxxxxxxxx
> > [mailto:linux-net-owner@xxxxxxxxxxxxxxx] On Behalf Of Matt Zagrabelny
> > Sent: Wednesday, May 28, 2008 2:45 PM
> > To: linux-net@xxxxxxxxxxxxxxx
> > Subject: connecting two hosts with crossover cable and autonegotiation
> >
> > Greetings,
> >
> > I am working on creating a GNU/Linux HA cluster and have a (non-gig)
> > crossover cable connecting eth2 on both nodes. The question I have is
> > how do cards like this auto-negotiate. They are negotiating to 10/half
> > whereas I would expect them to negotiate to 100/full.
> >
> > Some details:
> >
> > Debian GNU/Linux Etch
> > # uname -a
> > Linux squash 2.6.18-6-686 #1 SMP Thu May 8 07:34:27 UTC 2008 i686
> > GNU/Linux
> >
> >
> > The NICs on both nodes are 3Com 10/100:
> >
> > Ethernet controller: 3Com Corporation 3c905C-TX/TX-M
> > [Tornado] (rev 6c)
> > Subsystem: 3Com Corporation 3C905C-TX Fast Etherlink for PC Management
> > NIC
> >
> > Here are the results of 'mii-tool'.
> >
> > node1# mii-tool -v eth2
> > eth2: no autonegotiation, 10baseT-HD, link ok
> > product info: vendor 00:10:18, model 23 rev 4
> > basic mode: autonegotiation enabled
> > basic status: autonegotiation complete, link ok
> > capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
> > advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
> > flow-control
> > link partner: 10baseT-HD
> >
> > node2# mii-tool -v eth2
> > eth2: link ok
> > product info: vendor 00:10:18, model 23 rev 4
> > basic mode: autonegotiation enabled
> > basic status: link ok
> > capabilities: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
> > advertising: 100baseTx-FD 100baseTx-HD 10baseT-FD 10baseT-HD
> > flow-control
> >
> >
> > Here are the results of 'mii-diag'.
> >
> > node1# mii-diag eth2
> > Basic registers of MII PHY #24: 3000 782d 0040 6174 05e1 0021 0000
> > 0000.
> > Basic mode control register 0x3000: Auto-negotiation enabled.
> > You have link beat, and everything is working OK.
> > Your link partner is generating 10baseT link beat (no
> > autonegotiation).
> > End of basic transceiver information.
> >
> > node2# mii-diag eth2
> > Basic registers of MII PHY #24: 3000 780d 0040 6174 05e1 0000 0000
> > 0000.
> > Basic mode control register 0x3000: Auto-negotiation enabled.
> > You have link beat, and everything is working OK.
> > Your link partner does not do autonegotiation, and this transceiver
> > type
> > does not report the sensed link speed.
> > End of basic transceiver information.
> >
> > So why are the results of 'mii-tool' and 'mii-diag' different (I would
> > expect the same)?
> >
> > Is it possible for these types of cards to autonegotiate to 100/full?
> > How?

> You might have a bad PHY. You might have a bad cable. If you flip the
> cable around, does the output of mii-tool on the two ports flip around
> too? If so, suspect the cable since that would happen if one of the
> twisted pairs was bad.

I did try flipping the cable around and the output was the same. I also
tried a gig-crossover cable and that did not change the outcome either.

I suspect it is a bad PHY. I attempted to pin the speed/duplex to
100/full (on both hosts) and neither node could ping the other node,
though I could at 10/half.

I have since abandoned these cards and purchased two gigabit ones - they
autonegotiate to 1000/full without issues.

Thanks for the info and assistance.

Sincerely,

--
Matt Zagrabelny - mzagrabe@xxxxxxxxx - (218) 726 8844
University of Minnesota Duluth
Information Technology Systems & Services
PGP key 1024D/84E22DA2 2005-11-07
Fingerprint: 78F9 18B3 EF58 56F5 FC85 C5CA 53E7 887F 84E2 2DA2

He is not a fool who gives up what he cannot keep to gain what he cannot
lose.
-Jim Elliot

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