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mediaopt full-duplex DOES NOT work..
Authored by: jfanelli on Sep 14, '02 12:17:14PM

Folks, you have been able to issue the command to force duplex since 10.0, problem is, it doesn't do anything.

sudo ifconfig en0 mediaopt full-duplex

will appear to execute, but it doesn't actually force the duplex setting. I have verified this on 3 macs, my Beige G3 (with 3rd party 10/100 card), my G4/733 DA, and my TiBook550.

I have these connected to a Cisco 2924XL ethernet switch, where I have likewise force 100/Full Duplex on the ports in question. Even after issuing the force duplex command, and ifconfig en0 still shows the autonegotiated half-duplex setting. Of course, none of my PC's have problems negotiating duplex, and in typical windows fashion, you can force every conceivable NIC setting on Windows 2000 anyway. A full-duplex ethernet Sniffer (I work for Network Associates) on the link verifies this.

Autonegotiation not working well is not Apple's problem alone, many cards and switches have problems negotiating duplex. What is Apple's problem is its unique blindness to the fact that such settings should be configurable by advanced users and network administrators.

I love Jaguar, but network performance, and especially file sharing is still pathetic.

Jeff Fanelli

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mediaopt full-duplex DOES NOT work..
Authored by: dpfaust on Sep 18, '02 01:58:57PM

I found this problem as well. It appears that you have to supply both link speed and duplex for it to take in OSX 10.2. I ran the following first:

ifconfig en0 mediaopt full-duplex

and got the same results you did.

I then ran this:

ifconfig en0 media 100baseTX mediaopt full-duplex

and got the desired results.

Now my question is, how do I set this so that it happens automatically at boot time? I know that you can set some options in the /etc/iftab file. Currently my iftab file has this line:


Should I change it to this:

en0 media 100baseTX mediaopt full-duplex



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mediaopt full-duplex DOES NOT work..
Authored by: ScienceMan on Oct 31, '02 07:12:30PM

I would also like to make these settings -- did this work for you?

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mediaopt full-duplex DOES NOT work..
Authored by: carsten on Sep 21, '02 09:48:09AM

I checked system.log in the Console and it reports that my ethernet is indeed still only running at half-duplex. :( Well the lesson here is: just because you don't get an error message anymore don't assume it's working.

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mediaopt full-duplex DOES NOT work..
Authored by: jdos2 on Oct 04, '02 09:40:22PM

Indeed there are many cards that don't honor user settings, including systems such as AIX and their implementation of Token-Ring adapters.

The problem, or not, depending, is if the port and system aren't reporting errors, the negotiation was successful and things are probably working find, albiet wrong.

Besides, one can point to plenty of bad decode info even in the newest versions of Sniffer...


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mediaopt full-duplex DOES NOT work..
Authored by: jlneemidge on Oct 10, '02 04:25:24PM
File sharing I can understand, but I'm not sure about the gripe about network performance. I routinely saturate 100baseT ethernet from my laptop (PBG3 Firewire -- Pismo). It keeps pace just fine with AIX systems at work, and AIX has a _very_ good network stack.

I see no particular problems with Jaguar, at least on my hardware, with either network throughput or latency. I do agree that, e.g., ifconfig should actually do what it's told to do, but I don't see performance issues.

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mediaopt full-duplex DOES NOT work..
Authored by: Mr_Britt on Jan 28, '03 12:12:10PM
I have just gone through the same problem with our network of Mac's and PC's. We have both Cisco Catalyst 35xx-XL's and 29xx-XL's in our network that are interconnected using Gigabit Fibre. You need to stop the spanning tree protocol at port startup in these switches for the Mac's to autonegotiate the link correctly. To do this either use the Cisco Cluster Management Suite (CMS) to turn ON PortFast and set Duplex and Speed to Auto, or add the following to your ports config using telnet:
interface FastEthernet0/4      %% Your interface here
 description MacTest           %% port name
 switchport access vlan 4      %% vlan its in
 spanning-tree portfast        %% This is the only nonstandard option
!                              %% and stops STP from delaying port/link startup
This has fixed most of our network issues with Mac's and all the NIC's report the correct duplex and speed at both the switch and the machine. Hope this helps.

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mediaopt full-duplex DOES NOT work, but...
Authored by: atrusler on Feb 26, '03 03:08:07PM

I got this to work on an XServe and a G-4, but not on my G-3. You have to have the media option and the mediaopt option in the command or it will not do anything. For example:

ifconfig en0 mediaopt full-duplex

does nothing. but:

ifconfig en0 media 100baseTX mediaopt full-duplex

works like a charm. You can verify this by ifconfig. If autoselect is still showing up next to the media type, it did not work.

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