Ethernet slow one way?
- Thread starter zaxcom
- Start date
Zammy-Sam
Desertchild
btoneill
keeper of the cheese
This sounds like a classic example of what can happen when there is a duplex mismatch. Most likely your Mac is set to half-duplex, and the switch is set to full-duplex. Can you run 'ifconfig -a' from both the box that is slow, and from a box that is fast? Also, what model is your linksys router/switch?
Brian
Brian
Well I think I have traced the problem. After redoing the cables and not having any improvement I decided to bring the machine downstairs and hook it up with a known crossover cable directly to my main G4.
The problem is still there. So its not the router or the cabling going thru the house. Its the machine itself. I did ifconfig -a and confirmed that all machine are indeed in full duplex/100.
I guess the ethernet port on the imac is messed up. Not much I can do about that though, short of replacing the mother board.
The problem is still there. So its not the router or the cabling going thru the house. Its the machine itself. I did ifconfig -a and confirmed that all machine are indeed in full duplex/100.
I guess the ethernet port on the imac is messed up. Not much I can do about that though, short of replacing the mother board.
I had the exact same problem, and found a solution. It wasn't a duplex mismatch (managed switch so I could see exactly what it was doing), or a bad cable. Force the switch side to 10/full.
My story is here:
http://seth.mattinen.org/main.php?section=aenet
My story is here:
http://seth.mattinen.org/main.php?section=aenet
Unfortunately for me I have no way to force my switch. I am using a Linksys BEFSR41 Router and it does not have any provision I am aware of to control its speed or connection protocols.
I guess my only recourse is to take the iMac back down to OS 9. A real bummer since managing one OS in my small network was so much easier than two.
I guess my only recourse is to take the iMac back down to OS 9. A real bummer since managing one OS in my small network was so much easier than two.
Ripcord
Senior Lurker
Okay, just re-reading. If you have no way to force your switch to a certain speed or duplex, how can you be sure that it's running at 100/Full?
Also, forcing your NIC to 10/Full (referring to your other thread in the Networking forum) WILL result in a duplex mismatch if your switch/router is set for auto (which I'm almost positive it is). If you were going to try anything, I'd say try forcing the NIC to 100/half or 10/half.
Also, changing speeds to 10mbit really shouldn't "solve" the problem, it's just a sign that something else is wrong (usually faulty wiring, or that by changing the setting you actually got rid of another problem, like a duplex mismatch... Or, like Seth says on his webpage, it could just be a driver issue)
I've also run into some situations where 100mbit (or usually gigabit) systems manage to over-drive the system at the other end, which causes packet loss (either on the NIC, in the driver, or on the switch). Reducing link speed will avoid the issue, but usually a better solution is to reduce TCP window sizes, application block sizes, or whatever, to "throttle" the machine that's overwhelming.
Seems like this would be opposite in your case as well - the iMac would be the LEAST likely to overdrive. But then, if it's a possibility and you haven't found the REAL problem, I never eliminate it.
Also, forcing your NIC to 10/Full (referring to your other thread in the Networking forum) WILL result in a duplex mismatch if your switch/router is set for auto (which I'm almost positive it is). If you were going to try anything, I'd say try forcing the NIC to 100/half or 10/half.
Also, changing speeds to 10mbit really shouldn't "solve" the problem, it's just a sign that something else is wrong (usually faulty wiring, or that by changing the setting you actually got rid of another problem, like a duplex mismatch... Or, like Seth says on his webpage, it could just be a driver issue)
I've also run into some situations where 100mbit (or usually gigabit) systems manage to over-drive the system at the other end, which causes packet loss (either on the NIC, in the driver, or on the switch). Reducing link speed will avoid the issue, but usually a better solution is to reduce TCP window sizes, application block sizes, or whatever, to "throttle" the machine that's overwhelming.
Seems like this would be opposite in your case as well - the iMac would be the LEAST likely to overdrive. But then, if it's a possibility and you haven't found the REAL problem, I never eliminate it.
From what i have read in others posts, this is a known problem with 333 imacs running osx. Sure enough when i rebooted the machine into os9 100 full duplex ran just fine. No erros and full speed in both direction.
I know the machine is in full duplex 100 because the lights on my switch say it is, also ifconfig -a also confirms that the NIC is running at 100/full. Plus I put a monitor on the line and it also confirmed the data rate. The whole problem seems to come down to a bad driver in OSX programming. It causes a massive amount of CRC errors on data transmissions. The imac uses a bmac chipset for ethernet, where most other machines us a gmac chipset. The instructions to this chip are a little different. Appple knows about the problem I have been told, but since this machine is so out of date they have little incentive to rewrite the code for it.
I know the machine is in full duplex 100 because the lights on my switch say it is, also ifconfig -a also confirms that the NIC is running at 100/full. Plus I put a monitor on the line and it also confirmed the data rate. The whole problem seems to come down to a bad driver in OSX programming. It causes a massive amount of CRC errors on data transmissions. The imac uses a bmac chipset for ethernet, where most other machines us a gmac chipset. The instructions to this chip are a little different. Appple knows about the problem I have been told, but since this machine is so out of date they have little incentive to rewrite the code for it.
Well I have one last idea. Since I cant force 10/Full on the iMac by way of any command, I am going to force it by way of a hub. I am going to insert a 10Mbps hub in between the iMac and the Router. That should force the iMac to drop down to 10/Full from 100/Full.
I will let you all know later if it worked.
Zax
I will let you all know later if it worked.
Zax
I put a 10Mbps hub in the path and it all works great now. While the speed is limited to about 9Mbps. It is consistant in both directions. No more stalls or CRC errors. Since my cable modem connection is only 2Mbps it really does not matter that the iMac is on a slower port than the other machines.
