iMac IP Address keeps changinging

Question

Level 1

8 points

iMac IP Address keeps changinging

Hello all -

I recently made the change from Verizon (Frontier) to Time Warner. When the TWC tech connected me, he did so using a router only whereas Verizon used an Ethernet cable. The day of install, all worked as was expected. However, lately when I try to use the internet, the IP address changes from 192.168.x.x. to 169.254.x.x which goes nowhere. I check my wife's computer, my laptop, and both of our phones...all working really good, and fast, just not mine.

Has anyone experienced this?

I can go into System Preferences and see all of the settings under the Advanced tab and see the IP address of 169.254.x.x. By turning the wifi off and then back on, it instantly resets, gives me an IP of 192.168.x.x. What would cause this and can it be, or is there a fix? Any tips, tricks, or ideas will be greatly appreciated.

Is there a network adapter in a mac like there is in a PC? BTW - OS X 10.11.4

Thank you

Posted on Apr 11, 2016 7:46 AM

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Answer 1

Rudegar

Level 10

181,242 points

Apr 11, 2016 7:57 AM in response to JAberle

yes there is and they use the same network chips

which one you can see by clicking the apple menu and choosing about this mac->system report->ethernet cards

maybe you can fix your issue with resetting pram OS X Yosemite: Reset your computer’s PRAM

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Answer 2

Duane

Level 10

124,293 points

Apr 11, 2016 10:17 AM in response to JAberle

An IP address starting with 169 indicates that the iMac has assigned itself an IP address because it couldn't get one from a DHCP server.

You said that TWC supplied a router.

- Are you certain that it is a router or is it a modem only?

- If it is a router, are you certain that it is configured with the DHCP server enabled?

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Answer 3

dwb

Level 7

33,298 points

Apr 11, 2016 11:23 AM in response to JAberle

As Duane said your computer is getting a self assigned IP when you first start up. This can happen for a number of reasons some of which I know and understand - others leave me scratching my head but this procedure usually works. Open System Preferences, select Network. Select WiFi in the left window pane if it isn’t already selected and then click on the Advanced button. You’ll see a list of Preferred Networks. Delete them all. Make sure the Remember networks this computer has joined option is checkmarked. Click on OK and then click on Apply.

Now turn WiFi off using the menu item. Turn off the computer, then turn off the WiFi router. (Make sure you let everyone know you are doing this or someone might get very angry.) Wait about 15 seconds then turn the router back on. Wait about a couple minutes to make sure the router is functioning again then turn on the computer. (I usually check with my iPhone.) Turn WiFi back on. You’ll have to select the WiFi and maybe enter the password. Assuming the computer connects and you are online you may immediately test that the computer can be restarted etc and pick up the WiFi with a real IP.

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Answer 4

JAberle Author

Level 1

8 points

Apr 11, 2016 12:41 PM in response to Rudegar

Thanks...I'll give that a shot when I get in from work tonight...

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Answer 5

JAberle Author

Level 1

8 points

Apr 11, 2016 12:46 PM in response to Duane

Hi Duane,

Yes it is a router. This is really weird because my wife has a iMac a foot from mine and connects with no issues and has an IP of 192.168.x.x I'll try what Rudegar and dwb suggest...that's all I can do. I'll post back tomorrow with results one way or the other...Thanks to all

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Answer 6

Duane

Level 10

124,293 points

Apr 11, 2016 2:34 PM in response to JAberle

Check the settings on your router. If the DHCP server is disabled it will provide one (1) valid IP address. You machines will fight over it.

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Answer 7

JAberle Author

Level 1

8 points

Apr 11, 2016 5:23 PM in response to Rudegar

Hi Rudegar. This worked. Thanks. I just got home and when I tried to get online, IP had changed. Had to turn wifi off and then back on. Reset PRAM as per the instructions. Will get what work done tonight I can and will report back in the AM...

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Answer 8

JAberle Author

Level 1

8 points

Apr 12, 2016 9:50 AM in response to JAberle

Hi Rudegar,

UPDATE - This morning, PC and phone were both able to connect to internet. After working on the internet for about 3 hours last night, wifi signal and IP address were lost to all devices. Spoke with TWC. Support says modem/router was working. She indicated that she changed the router signal from automatic to Channel 9 to clear up any possible signal static. Worked fine for the remainder of the evening.

This morning I have an IP address on the iMac of 169.254.x.x All other devices have an IP of 192.168.x.x and all are working okay. I will try dwb's suggestion tonight but I can already tell it may not work. Once I reset the router/modem (Yes Duane, I asked and that's what the tech referred to it as) I know it will reset the IP address so I'm not putting too much faith into this being the fix, but I will try. When I turn Wifi off and then right back on, the correct IP is assigned and I can once again get online, but that doesn't help when the work your doing online is on the screen in front of you...and you know as soon as you cycle the wifi, you're starting all over because you just never quite made it to the save button before you lost the connection...So frustrating!

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Answer 9

Duane

Level 10

124,293 points

Apr 12, 2016 10:01 AM in response to JAberle

What is the make and model number of this router/modem device?

Have you accessed the settings page of the router/modem? Assuming that your VALID IP address is 198.168.1.x, you should be able to access the router login at 192.168.1.1.

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Answer 10

JAberle Author

Level 1

8 points

Apr 12, 2016 12:38 PM in response to Duane

I believe the make is an Arris, the model I'm not certain of, but I will get that info for you when I get home this evening. Because I don't know will I ask...If other devices are able to connect through the router/modem, wouldn't it stand to reason the problem will be in the iMac rather than the router/modem setup

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Answer 11

Duane

Level 10

124,293 points

Apr 12, 2016 12:43 PM in response to JAberle

Switching ISPs should not cause difficulty for your iMac. It could be the iMac but is very likely the Arris.

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Answer 12

JAberle Author

Level 1

8 points

Apr 13, 2016 12:32 PM in response to Duane

Because of the way the modem/router is mounted with label against wall, I decided not to remove it from the wall. Here's where things stand so far. All of the suggestions for fixes, and I appreciate every one of them, have not worked. Last night I "Shut Down" rather than log off. This morning internet woke right up. Then I logged out and within the time it took to log out and back on, the IP address had changed again and would not connect. I turned wifi off and then back on...good connection once again.

Recent upgrade from 10.11.3 to .4 but I'm sure that's not the problem and the router/modem seem less suspect now than when they did on the 5th, when TWC setup shop in my garage...after all, if every other device I have can connect, except my iMac, chances are it's in the software somewhere in my iMac. But then again, my wife's computer has the same OS.

I will need to be content to shut down or switch wifi off and on.

Thank you again to all who offered suggestions. Greatly appreciated...

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