New iMac and Duplex

Question

Level 2

179 points

New iMac and Duplex

Good day,

I recently purchased a new 24" iMac 2.8G Mac. It is a thing of beauty. It replaced my old G5. If I allow the network configure the Ethernet settings automatically it drops to half-duplex.

The G5 and all other devices connected to my hub auto select full-duplex. I have changed ports, rebooted, etc. No dice. Unless I force full-duplex it drops and runs at half.

Has anyone else experienced this problem?

Here it is forced to full duplex:

en0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
tunnel inet -->
inet6 fe80::21b:63ff:fe9e:717c%en0 prefixlen 64 scopeid 0x4
inet 10.10.10.10 netmask 0xffffff00 broadcast 10.10.10.255
ether 00:1b:63:9e:71:7c
media: 100baseTX <full-duplex> status: active
supported media: autoselect 10baseT/UTP <half-duplex> 10baseT/UTP <full-duplex> 10baseT/UTP <full-duplex,hw-loopback> 10baseT/UTP <full-duplex,flow-control> 100baseTX <half-duplex> 100baseTX <full-duplex> 100baseTX <full-duplex,hw-loopback> 100baseTX <full-duplex,flow-control> 1000baseT <full-duplex> 1000baseT <full-duplex,hw-loopback> 1000baseT <full-duplex,flow-control> none
vlan: 0 parent interface: <none>
bond interfaces: <none>

Thanks

iMac 2.8, PowerMac G5, Graphite Clamshell, MacBook Pro, Mac OS X (10.4.10), iPhone, Windoze.....

Posted on Sep 13, 2007 2:11 AM

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Answer 1

ScartArt

Level 1

25 points

Sep 13, 2007 2:28 AM in response to Alex Neil

This sounds like an issue with the device it is connected to. For auto negotiation to work both ends need to be configured to support it. If your iMac doesn't communicate with the other device it will drop to half duplex.

I assume the device at the other end is a switch and not a hub? Does that device fully support auto neg?

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Answer 2

Alex Neil Author

Level 2

179 points

Sep 13, 2007 4:00 AM in response to ScartArt

It's a HOTBRICK LB2 Firewall/Router with a 4 port switch. I've been using it for several years. Also plugged into it are a PC, a G5 and a Cube. All of those are set to autonegotiate and remain at full-duplex. I did move the new iMac from port to port to see if the problem persists. It does...

Thanks

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Answer 3

Alex Neil Author

Level 2

179 points

Sep 13, 2007 4:03 AM in response to Alex Neil

btw - at work we use CISCO switches and all our G5's and MacBook Pros have to be forced to full-duplex. Maybe it's the onboard ethernet on the Macs that isn't as compatible as dumber PCs, etc.

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Answer 4

ScartArt

Level 1

25 points

Sep 13, 2007 5:46 AM in response to Alex Neil

There shouldn't be an issue with Macs and Cisco switches. I possibly could understand the G5s but not new MacBook Pros, these sort of incompatibilities were mainly sorted out years ago.

The problem with forcing to 100 full is the other end also needs to be forced, otherwise that switch will drop to half duplex resulting in a reduction in performance.

Have you contacted Apple? Hopefully a driver update will fix your issue.

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