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iMac has resurrected 'Ethernet Self-Assigned IP address" error! Back to Windows?..

alexjholland

alexjholland

macrumors 6502a
Original poster
May 3, 2011
858
877
Bali, Cambridge, Sydney.. anywhere.
Hey, I bought the Quad-core i7 2010 iMac about four months ago. I posted here perhaps two months ago when I got the somewhat infamous 'Ethernet has a self-assigned IP address and will not be able to connect to the Internet" error.

Google trawling suggests this error has appeared for various people at random times and appears to have NO guaranteed fix. It's been repeatedly suggested it is a serious coding error that has existed since 2003; certainly the number of people who have been forced into system re-installs would testify to this.

Fortunately, this error seemed to fix itself - but today the problem has returned.

- I have tried deleting the file com.apple.alf.plist from preferences today, which worked briefly - then the error returned.

- I also tried resetting my PRAM and NVRAM settings by holding a sequence of keys at startup. Again, no difference.

My internet runs via ethernet, underneath floorboards, from my hallway Linksys ADSL router, to a Netgear 8-port managed router in my bedroom, where it is distributed to a host of other machines that happily work - the entire network is Gigabit also.

I am now using the wireless connection from our hallway Linksys, which works fine for browsing - but I must have an ethernet connection for the streaming I do.

I spent £2,000 on this machine. I expect everything to work. Broken ethernet is broken ethernet; regardless of whether it is a software or hardware error.

I get very little spare time from work/training, I certainly do NOT have much time to fiddle around with computer; and am going to return this iMac, demand a refund and get another Windows machine if I can't find a solution.

I have used Windows for 15 years and never dealt with such a serious, unreasonable error as this. I heard Macs were more efficient and good for people who do not have the time or inclination to waste fiddling around with computer problems; but I've spent more time on this problem than any computer deserves.

Also, I will NOT be disassembling my iMac and plugging it into the router upstairs, to see if the problem is a router that happily works with every other device I own - if it comes down to this I'll simply return it and go back to Windows.

If anyone has any ideas for anything I can trying doing with the software then I'll give it a go this weekend.

Here is a screenshot I took when my ethernet was working fine last time:
http://i1203.photobucket.com/albums/bb385/alexjholland/EthernetWorking2011-04-24at180756-1.png
Here is a screenshot of how it currently looks. I've tried typing in the same details from when it was working, but this doesn't help..
http://i1203.photobucket.com/albums/bb385/alexjholland/Screenshot2011-06-11at144650.png
 
Ok, called Apple support (turns out I have five days of complimentary phone support left) ran through a bunch of settings ideas and ran network utility from the install disc - none of which worked.

They then said to try switching the Switch in my bedroom over to another one; I did and it works. So I'm thinking ok, my Netgear switch is at fault - but then I switched back to the Netgear switch and it works!

So I'm back to having working ethernet, but for how long? And why didn't it work until I not only turned off the Switch (tried this earlier) but completely unplugged everything and replugged it back in?

If I call up next weekend with the same problem, they'll charge me £35!

Feel like a piano's hanging over my head.. I've already missed out on work for next week; I'm self-employed, direct financial implications - not impressed!
 
alexjholland said:
Ok, called Apple support (turns out I have five days of complimentary phone support left) ran through a bunch of settings ideas and ran network utility from the install disc - none of which worked.

They then said to try switching the Switch in my bedroom over to another one; I did and it works. So I'm thinking ok, my Netgear switch is at fault - but then I switched back to the Netgear switch and it works!

So I'm back to having working ethernet, but for how long? And why didn't it work until I not only turned off the Switch (tried this earlier) but completely unplugged everything and replugged it back in?

If I call up next weekend with the same problem, they'll charge me £35!

Feel like a piano's hanging over my head.. I've already missed out on work for next week; I'm self-employed, direct financial implications - not impressed!
Click to expand...

Not impressed with what? They helped you narrow it down to a possibly intermittent switch problem. If the voltage on the power supply of the switch is marginal it will can give some problems that would have you chasing your tail, I've had it happen before. Blaming your iMac for this would be the same as blaming your car for running crappy because of bad gasoline.😕
If there is a problem, with your hardware, Apple customer service is pretty good. If you reported this problem before your warranty period was up, and it turns out to be a bad ethernet port on your iMac, they'll probably help you out.
 
Ok, I've just got an ethernet cable and plugged my Macbook into the back of my switch - it also gets self-assigned IP address!

So logically, if both Macs get the same 'self-assigned IP' error, on two different switches, all connected to the same ADSL router in my hallway:

- The most logically likely explanation is a problem with my ADSL router in the hallway.

- There is a possibility that both machines have the same error simultaneously, but this seems unlikely.

So what could I possibly change on the ADSL router in the hallway to affect this?

Ideas appreciated - failing this I'll just do a factory reset and see if it works!
 
alexjholland said:
Ok, I've just got an ethernet cable and plugged my Macbook into the back of my switch - it also gets self-assigned IP address!

So logically, if both Macs get the same 'self-assigned IP' error, on two different switches, all connected to the same ADSL router in my hallway:

- The most logically likely explanation is a problem with my ADSL router in the hallway.

- There is a possibility that both machines have the same error simultaneously, but this seems unlikely.

So what could I possibly change on the ADSL router in the hallway to affect this?

Ideas appreciated - failing this I'll just do a factory reset and see if it works!
Click to expand...

Do you have any type of MAC filtering in your router?
Does your DCHP server have a max number of clients setup?
Does your Router have any type of logging for the DHCP table?
Have you tried assigning a static IP address in your subnet just to see if its a DHCP problem?
 
- We have a 'wireless MAC filter'. Firstly it's purely ethernet we have problems with; and secondly it's off.

- Maximum Number of DHCP Users: 50

- No idea?

- You mean do this in my iMac's System Prefences/Network? Yes, I tried typing in the settings that were in place when it worked in the past. It gave me a green light - but wouldn't work.

Moreover, seeing as both the iMac and Macbook have the same issue, I would - humbly - conclude the issue must be in the ADSL router?
 
Solution!

So problem turned out to exist with two Apple computers; making it unlikely to be them both causing the error simultaneously.

It still occurred with two different switches in my bedroom; again, just about eliminating them as the cause.

Then finally, I dug out our old ADSL router and found the same problem existed with two different routers! So each stage of hardware tested and just about eliminated!

By plugging my Macbook in at different points of the cabling to see if it worked, I ascertained the problem lay in the length of cable running down to my bedroom.

Turns out, the RJ45 connector that terminates in our hallway is slightly broken and won't stay in properly on the ADSL router. A piece of blu-tack wedged in did the job.

My Windows computer used to say 'network connection unplugged', even if it was two or three routers away. I now know that this self-assigned IP address error can mean a number of things, including a faulty/unplugged cable!

Glad this seems to be sorted, although recommend anyone else (and Apple's helpline!) are aware that this issue can, sometimes, be as simple as a cable!
 
Everything in my bedroom network is Cat 6. The cable running down to my room is Cat 5e, but that can't easily be replaced as it was laid when we put down a wooden floor!

We are moving this year though; and I'll be taking a powerdrill, some ethernet sockets and many metres of Cat6 cable to our new house's walls!
 
alexjholland said:
I spent £2,000 on this machine. I expect everything to work. Broken ethernet is broken ethernet; regardless of whether it is a software or hardware error.

I get very little spare time from work/training, I certainly do NOT have much time to fiddle around with computer; and am going to return this iMac, demand a refund and get another Windows machine if I can't find a solution.

I have used Windows for 15 years and never dealt with such a serious, unreasonable error as this. I heard Macs were more efficient and good for people who do not have the time or inclination to waste fiddling around with computer problems; but I've spent more time on this problem than any computer deserves.

Also, I will NOT be disassembling my iMac and plugging it into the router upstairs, to see if the problem is a router that happily works with every other device I own - if it comes down to this I'll simply return it and go back to Windows.
Click to expand...

alexjholland said:
Solution!

Turns out, the RJ45 connector that terminates in our hallway is slightly broken and won't stay in properly on the ADSL router. A piece of blu-tack wedged in did the job.

My Windows computer used to say 'network connection unplugged', even if it was two or three routers away. I now know that this self-assigned IP address error can mean a number of things, including a faulty/unplugged cable!

Glad this seems to be sorted, although recommend anyone else (and Apple's helpline!) are aware that this issue can, sometimes, be as simple as a cable!
Click to expand...

Thanks for the entertainment. 😀

Protip: Switch != router.
 
alexjholland said:
Everything in my bedroom network is Cat 6. The cable running down to my room is Cat 5e, but that can't easily be replaced as it was laid when we put down a wooden floor!

We are moving this year though; and I'll be taking a powerdrill, some ethernet sockets and many metres of Cat6 cable to our new house's walls!
Click to expand...

Then consider getting a Gigabit Switch. I have two of the D-Link DGS-1008G 8-Port Gigabit Desktop Switch and they work great for me. I can share in my house at great speed.
 
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The problem is not your cables or network hardware

I do not know what it is or what causes it. I have had the same issue with my MBA on occasion, today being one of them. It will get the .169 IP address self assigned and then can not reach the Internet. I am at a cafe now, so can not power cycle their router. That nearly always fixes e problem at home. Right now, on Panera's network iPad 2 and iPhone 4 connect no problem, air gets the .169. If I join the Peets or nearby whole foods network the MBA has no problem. In the past same problem has happened to MBP, MBA and this iPad. Can find no reason why, it is why I was googling around today. Like I said. At home power cycling the router does the trick. You will find many threads on this topic out there, this site and others, including support.apple.com, dating back to at least 2008, but not a consistent, definitive solution. 😕
 
alexjholland said:
Sod off! Anyway Apple should have had an 'unplugged cable' icon like Windows did!
Click to expand...

For the record, Apple does use a "Cable unplugged" icon when it detects that, but when the cable is damaged like that, it may not actually recognize that it is unplugged because of the partial contact that will be made.

jW
 
same issue

I am having a similar issue with my MacBook Pro. I have been in France for a few weeks now, using the citywide free wifi. All of the sudden I am receiving a self assigned IP address and cannot connect. Needless to say, I have no control over the router, my roommate's macbook is working just fine on the network, and I am able to connect to other networks at the University. Please help!!
I have tried to manually set the IP, renew the lease, everything.
 
Yeah I think it seems pretty clear there is an issue. I was lucky mine was physical, but for those with wireless the solutions have not always happened.

And FYI, the damage was simply to the plastic clip that keeps the cable in. To all intents and purposes, the cable WAS unplugged.
 
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