User profile for user: Paul Fons
Paul Fons Author
User level: Level 1
84 points

Mac Pro and Jumbo frames

I am a little confused about the mtu setting on the ethernet interface on my Mac Pro (four core Xeon 2007 model). Under 10.4, I was able to select a mtu setting of jumbo (9000) in the network settings panel and it worked fine (I have a local gigabit router that handles jumbo frames). My MacBook Pro under leopard 10.5.2 is able to run with jumbo frames without problem on the same router, but the Mac Pro while it will let me select the jumbo frame item in the Network control panel, will not "stick" -- it resets automatically to standard (1500) or custom (1504). Using the /usr/sbin/networksetup -listvalidMTUrange en0 command my mac claims it can only be set from 72-1504. This is different than before when I was (or at least I think I was) using Jumbo frames. Any ideas as to what could be scrozzed (if anything)? I can't believe my MacBook Pro can use jumbo frames but the more expensive mac pro cannot. This is very frustrating. Any suggestions?

2.3 GHz MacBook Pro and Quad MacPro, Mac OS X (10.5.2)

Posted on Feb 13, 2008 7:07 PM

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User profile for user: Steven Whatley
Steven Whatley
User level: Level 1
95 points

Mar 4, 2008 3:02 PM in response to Steven Whatley

I managed to get jumbo frames settings to stick. I needed to disable the network interface and re-enable it. I got it set to 7418 bytes to match my Buffalo Terastation's max jumbo frame size. It seems to be helping throughput with the Terastation. I'm be kind of disappointed with the normal transfer speed of the Terastation. Turning on jumbo frames seems to help. Speeds has gone up from 4mbps to 13mbps.

Thanks,
Steven
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User profile for user: Scott Atchley
Scott Atchley
User level: Level 4
2,225 points

May 6, 2008 4:19 PM in response to Steven Whatley

This seems to be a bug in the System Preference's Network panel. If you check the mtu using ifconfig before trying to set the mtu and then check it again after setting it to 9000 (or another value), ifconfig reports the correct value even though the Network panel still says 1500.
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User profile for user: direwolf8
direwolf8
User level: Level 4
1,286 points

May 7, 2008 6:13 AM in response to Scott Atchley

This is an ongoing problem with additional ethernet ports on my G5. The built-in port works through the control panel settings, but I have to use ifconfig to set the add-on ports. They work correctly if I set them up that way, but the control panel doesn't reflect it.

Please report it as a bug. Maybe they'll finally get around to fixing it.
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Mac Pro and Jumbo frames

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