full-duplex / half-duplex switching, why?

full-duplex / half-duplex switching, why?

Post by Ted » Tue, 06 May 2003 16:29:38



i have rh 8.0 router with iptables and two nic's
eth0 is for local and eth1 for public network.

i can notice in messages something like this:
kernel: eth1: Setting half-duplex on MII #1 link partner capatibility
of 000
kernel: eth1: Setting full-duplex on MII #1 link partner capatibility
of 41e1

it happens more times per day, switching to half-duplex and then back
to full-duplex few minutes later.
why is that?

regards

 
 
 

full-duplex / half-duplex switching, why?

Post by Jim Kno » Tue, 06 May 2003 23:20:57


Because auto-sense Ethernet 10-100 full/half duplex does not work
flawlessly.  I suggest hard coding both sides of the connection.  See
if the message stops.

> i have rh 8.0 router with iptables and two nic's
> eth0 is for local and eth1 for public network.

> i can notice in messages something like this:
> kernel: eth1: Setting half-duplex on MII #1 link partner capatibility
> of 000
> kernel: eth1: Setting full-duplex on MII #1 link partner capatibility
> of 41e1

> it happens more times per day, switching to half-duplex and then back
> to full-duplex few minutes later.
> why is that?

> regards


 
 
 

full-duplex / half-duplex switching, why?

Post by David Efflan » Wed, 07 May 2003 09:04:37



> i have rh 8.0 router with iptables and two nic's
> eth0 is for local and eth1 for public network.

> i can notice in messages something like this:
> kernel: eth1: Setting half-duplex on MII #1 link partner capatibility
> of 000
> kernel: eth1: Setting full-duplex on MII #1 link partner capatibility
> of 41e1

> it happens more times per day, switching to half-duplex and then back
> to full-duplex few minutes later.
> why is that?

How many machines are you connecting to and what duplex are they?  For
example if this computer communicates with one device that is 10baseT half
duplex, it will switch to that.  If it then communicates with something
100baseT full duplex it will switch to that (assuming it is going through
a switch and not a hub).  Or it could be that it kicks back when not
communicating with anything.  mii-tool can be used to advertise or force
speed and duplex.  But forcing full duplex may break a connection with
something that only does half duplex (likewise for speed).

--
David Efflandt - All spam ignored  http://www.de-srv.com/
http://www.autox.chicago.il.us/  http://www.berniesfloral.net/
http://cgi-help.virtualave.net/  http://hammer.prohosting.com/~cgi-wiz/

 
 
 

full-duplex / half-duplex switching, why?

Post by Whoeve » Wed, 07 May 2003 09:29:48




> > i have rh 8.0 router with iptables and two nic's
> > eth0 is for local and eth1 for public network.

> > i can notice in messages something like this:
> > kernel: eth1: Setting half-duplex on MII #1 link partner capatibility
> > of 000
> > kernel: eth1: Setting full-duplex on MII #1 link partner capatibility
> > of 41e1

> > it happens more times per day, switching to half-duplex and then back
> > to full-duplex few minutes later.
> > why is that?

> How many machines are you connecting to and what duplex are they?  For
> example if this computer communicates with one device that is 10baseT half
> duplex, it will switch to that.  If it then communicates with something
> 100baseT full duplex it will switch to that (assuming it is going through
> a switch and not a hub).  Or it could be that it kicks back when not
> communicating with anything.  mii-tool can be used to advertise or force
> speed and duplex.  But forcing full duplex may break a connection with
> something that only does half duplex (likewise for speed).

No, you are completely wrong here!

The NIC establishes a link to one port of the switch. The characteristics
of that link are completely disconnected from where the Ethernet packets
are forwarded by the switch.

What appears to be happening is that something is causing the link to be
re-negotiated. Either end could initiate this. Perhaps the connection is
poor and this is causing one end to initiate a re-negotiation. Perhaps a
cable is being moved, causing a temporary disconnect?

Either way, unless you have a performance issue, don't worry about it.

One thing to look out for: NFS does not work at all well with a
half-duplex connection!

- Show quoted text -

 
 
 

1. half-duplex/full-duplex problem

I have a new Sun E10, that is connected to a network switch using a cat 3
cable. We had some problems getting the conenction to work, apparently the
machine and the switch could not agree on what speed to run at, so I have
manually set it to 10 MB.

However, I have noticed another problem, incoming traffic runs MUCH slower
than outbound, very noticeable with FTP.

It appears the line runs only half duplex. The network guys says the switch is
set for full duplex, but runs in half because the E10 requests it.

On the E10, I see the follwing, as I can understand from the manual. I have
not done much work with these settings, so I may miss something here.

It is set to do full duplex:
  # ndd /dev/hme 10fdx_cap
  1

No negotiation
  # ndd /dev/hme adv_autoneg_cap
  0

But it thinks the Link Partner (the switch, I presume) can not do
full duplex:

  # ndd /dev/hme lp_10fdx_cap
  0

But it reports it is doing full duplex.

  # ndd /dev/hme link_mode
  1

(I assume '1' means full, the manual is not real clear on that)

And it's set to only do full duplex.
  # ndd /dev/hme adv_10fdx_cap
  1
  # ndd /dev/hme adv_10hdx_cap
  0

Suggestions?

Thanks

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