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59310 Views 90 Replies Latest reply: Nov 16, 2010 6:20 AM by Pinthea
Currently Being ModeratedNov 17, 2009 12:45 PM (in response to Pinthea)I would ask Apple, you have 90 days support may as well use it. Other than that have you tried using the ifconfig command in terminal?
from the manual page:-
mtu n Set the maximum transmission unit of the interface to n, default
is interface specific. The MTU is used to limit the size of
packets that are transmitted on an interface. Not all interfaces
support setting the MTU, and some interfaces have range restric-
tions.iMac 20", Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 2:42 PM (in response to rack0 tack0)I did call support -- in fact I have an open ticket right now and am working with them to try and figure it out. Unfortunately they're not that familiar with MTU or jumbo frames and don't have a 27" Core i5 unit to test it out on, so I'm sort of out there hanging in the wind...
I'll try the ifconfig command line thing to see what I get, but as it points out "some interfaces have range restrictions" and my very issue is being limited to a range of 72 to 1500. Maybe it's a UI bug and it can be set otherwise via command line.iMac 27" Core i5, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 2:57 PM (in response to Pinthea)I have just tried it on my iMac 7,1 machine. It lets the custom be set from 72 to 9000 and checking in ifconfig confirms that its 9000. However the UI keeps displaying Standard 1500, not sure what is happening there, presume that is a UI bug.
I normally run with an MTU 1492 and if I set it to this the UI does display Custom 1492.
The ifconfig always seems to show the value that I set it to even when set from the UI.
I am running 10.6.2 , I presume if its a new machine yours is also 10.6.x
Hope you get the conformation that you can run 9000
regardsiMac 20", Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 3:53 PM (in response to rack0 tack0)OK, I've tried to use ifconfig from within terminal as follows:
The results show that an mtu value of 1500 is what's set currently.
So then I try this:
ifconfig en0 mtu 1500
(just to see if it's possible to set the value via ifconfig)
ifconfig: ioctl (set mtu): Operation not permitted
And in testing ifconfig further, ANY mtu value I supply, whether it be in the range of 72 - 1500 (which is what the UI says is allowed) or whether it be 9000 (as I want it to be), I get the same error.
If I use the system preferences/network advanced properties to use the UI to change MTU to another value within the displayed allowed range of 72-1500, say, 1492, then after applying the change I do see that ifconfig reports that MTU in its results when I query the attributes of en0. So the UI IS able to set the MTU value, as long as it's within the range of 72-1500, whereas I cannot set the MTU to a value within that range manually using ifconfig.
When I go back to network properties and look at the MTU field, I do see that it is displaying the correct value of 1492 if I set it to 1492 via the UI.
If I try to use the UI to set the MTU to a value higher than 1500, it ends up setting it to 1500 (which is confirmed by ifconfig).
I've tried resetting the SMC, resetting the PRAM, and even going into SAFE mode.
The ethernet chipset (Broadcom 5764) from what I can tell IS capable of jumbo frames; it would seem that the driver or ethernet support for it on my machine (and potentially other Core i5's) is lacking support for Jumbo frames or any MTU value > 1500.
I hope this is something Apple will be able to fix, I'll be sure to report this info to the Apple Care support guy I'm working with...iMac 27" Core i5, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 4:12 PM (in response to Pinthea)ifconfig is a privileged command, and if you already knew that, my apologies.
Have you tried invoking the command using "sudo"? That lets you run the command as root. I don't have my Mac with me here at work, but I would give that a try:
sudo ifconfig en0 mtu 9000
It'll prompt you for your password.20" iMac (mid 2007) 2.4GHz 4 GB, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 4:37 PM (in response to Scorpie)Rookie mistake, my bad!
You're right, sudo is what was required. Thanks...
I can use "sudo ifconfig en0 mtu xxxx" to set any mtu value between 72 and 1500. If I try any value > 1500, the result is always:
ifconfig: ioctl (set mtu): Invalid argument
So I am apparently lacking support for any MTU > 1500. No jumbo frames.iMac 27" Core i5, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 5:07 PM (in response to Pinthea)Ah, looks like you'll need to get the answer from the horse's mouth. The kernel must not understand that big value.20" iMac (mid 2007) 2.4GHz 4 GB, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 6:24 PM (in response to Scorpie)Disappointingly there was no joy from the Apple Care specialist I was working with. We tried almost everything. After I got off the phone with him I even tried a fresh install of Snow Leopard from the 10.6.2 DVD which came with it. As soon as I was able to login for the first time I went straight to the network settings where I was able to verify that from a fresh, clean install there is NO support for Jumbo Frames or any MTU > 1500.
Disappointingly and more alarmingly than that, I tried to perform the Apple Hardware Test (AHT) by booting with the Applications Install DVD and pressing and holding D at boot, and once the AHT disc loaded the screen flashed and the system powered off.
And then it happened again when I tried it again.
And then it happened yet again when I tried it again.
But it boots fine and seems to run fine except for its complete inability to run the AHT utility.
So I've got a Genius Bar appt for Thursday afternoon to have them look at it.
And disappointingly, I'm not impressed with my experience with this new computer. Maybe this is the price I pay for being an early adopter. But frankly I expect to at least be able to run the diagnostics utility!!!
Message was edited by: PintheaiMac 27" Core i5, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 6:18 PM (in response to Pinthea)One question I have is: Were you running Leopard or Snow Leopard on your previously owned iMac?MacBook Pro 15-inch 2.2Ghz SR / iMac G5 (iSight) 2.1Ghz, Mac OS X (10.5.8), iMac G3 500Mhz 10.4.11 / iPod 3G 20GB / 5G 80GB
Currently Being ModeratedNov 17, 2009 6:26 PM (in response to StephenCCH)Snow Leopard, 10.6.1. Just got rid of that 24" iMac a week or two ago...
Key differences -- New Intel chipset with the i5 as compared to what might have been on the 24" model. If I'm not mistaken, the 24" model used an nVidia chipset and those awful integrated 9400 graphics.iMac 27" Core i5, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 7:32 PM (in response to Pinthea)There was only one model of the 24-inch iMac that ever used the Nvidia 9400m graphics and that was the $1499 US priced Early 2009 model.
All iMacs since 2006 (Intel) has had support for jumbo frames. On Apple's current online web site only the Mac Pro out of all current Macs has Jumbo frames specifically stated in the Tech Specs.
I am going to check the developers section for Hardware specs and see if they have them up yet. This could answer this question very quickly.
Message was edited by: StephenCCHMacBook Pro 15-inch 2.2Ghz SR / iMac G5 (iSight) 2.1Ghz, Mac OS X (10.5.6), iMac G3 500Mhz 10.4.11 / iPod 3G 20GB / 5G 80GB
Currently Being ModeratedNov 17, 2009 7:47 PM (in response to StephenCCH)Yep, that's (was) my iMac.
24", 1920x1200, integrated nVidia 9400m graphics, 2.66 GHz C2D.
Was a good system, a little pokey for what I needed it for (video encoding).
Would appreciate what you can find out.
THANKS!!!iMac 27" Core i5, Mac OS X (10.6.2)
Currently Being ModeratedNov 17, 2009 8:11 PM (in response to Pinthea)Unfortunately nothing from the developer section. If I find anything about this though I will post here. Hopefully Apple can find out for you. If they do, please tell us as this would be a downgrade not an upgrade for the ethernet port.
All other Macs seem to support Jumbo Frames according to the app Mactracker.MacBook Pro 15-inch 2.2Ghz SR / iMac G5 (iSight) 2.1Ghz, Mac OS X (10.5.6), iMac G3 500Mhz 10.4.11 / iPod 3G 20GB / 5G 80GB
Currently Being ModeratedNov 17, 2009 8:18 PM (in response to StephenCCH)I can't imagine that the Broadcom chip they use isn't jumbo frame capable, it must be an issue with the driver or ethernet chipset support in the kernel.
Hopefully they can address it with a future software udpate...
I'm curious to examine the new C2D iMacs (both the 21.5" and 27") to see if any of them have Jumbo Frames as an option. I know it's not necessarily apples-to-apples since there are different chipsets and motherboards at play, but if Jumbo is an option there then there can't possibly be an intent for Apple to disable it on the i5's...
Sigh...iMac 27" Core i5, Mac OS X (10.6.2)