10 Replies Latest reply: Oct 25, 2014 5:40 PM by Kippster2012
David Stahl Level 1 (0 points)

A few days ago our power went out for a few hours during the middle of the day. I returned home after work by which time the power had been back on for 3 or 4 hours. My wife told me that our internet wasn't working. I figured that I just needed to restart the router and/or modem, but that didn't fix it.


If I plug a laptop into the cable modem, I can get online just fine.


If I plug the Airport Extreme into the modem, the Airport Utility says that the base station does not have a valid ip address and then it tells me that the DNS servers aren't configured.


I've tried restoring both the modem and the base station to factory defaults and powering them down. I bring up the modem and wait for all of the lights to come on. Then I bring up the airport extreme while the ethernet cable is plugged into the modem and configure it like so:


  1. I name it and set the password
  2. I want to create a new wireless network
  3. Set the SSID and password
  4. Share a single IP address using DHCP and NAT
  5. Do not enable guest network
  6. I use a DSL or Cable Modem with a static IP address or DHCP
  7. Configure IPv4 Using DHCP
    1. The IP address as shown is and the subnet mask is I'm guessing this doesn't matter at this point? Everything else is blank.
  8. Then I select "Update"


The airport restarts and I connect to the new wireless network. I notice my amber light is flashing on the extreme.


AirPort Utility tells me I have two problems: my base station doesn't have a valid IP address and that there are no DNS servers.


The page that shows the ip address problem shows a blank IP address and a subnet mask of I can hit "Continue" to skip this and then enter (or not) some DNS servers.


No matter what, I can't get the Airport to get an ip address or get online. I have called Comcast earlier in the week and they claim my modem is working great. I'm about to call them back and see if they'll admit to changing anything.


I tried briefly to get this to work with an airport express that I have in case there's a real problem with my airport extreme. However I couldn't get the express to work, although I didn't spend too much time on it.


Anyone having similar problems or any other ideas to try? I'm located in Atlanta, Ga, in case there's something regional going on. Thanks for any and all suggestions.

  • John Galt Level 8 (45,943 points)

    Your modem is not distributing IP addresses. The address is "self-assigned" and worthless. As you indicated in step 7, nothing else is going to matter since your Extreme is not connected to the Internet.


    Your modem configuration and status pages ought to look like this:


    Screen Shot 2012-03-21 at 9.11.40 PM.png


    Screen Shot 2012-03-21 at 9.13.21 PM.png


    Regardless of what your cable company says if the modem is not distributing IP addresses it's not going to work. You might need to get them to replace it. Until then try powering it down for a good long time, at least several minutes, and let your Extreme rest also. Then, power up the modem, wait a few moments, followed by the Extreme and all other network devices in that order.


    It sounds as though you changed the Extreme's settings so you may have to verify them again after doing this. Following that it may be required to perform another power down exercise.


    Leave the Extreme connected to the modem during this power down. Connecting anything else to the modem will require that you power it down again so it "forgets" the device that was last using it.


    If all else fails, perform a "hard reset" on the Extreme. It is possible an internal parameter has become corrupted, in which case the "hard reset" is the only way to clear the fault.


    Make sure you do it properly so the "hard reset" is effective: http://support.apple.com/kb/HT3728

  • David Stahl Level 1 (0 points)

    Thanks for the reply, I'll try the extended power-down and let it sit over night. I will go through the original setup again before shutting it down and leave everything connected as you've suggested.


    I know that my laptop gets an IP address when I plug it directly into the modem. I've read on other forums that this motorola may not actually give out IP addresses but it may come from the ISP (Comcast)'s own DHCP servers somewhere else. Not sure if that's true, or if that was a change recently on their end?


    I should also add that my Surfboard diagnostic screens look like what you've posted and it does seem to work if I cut out the airport extreme.

  • John Galt Level 8 (45,943 points)

    In addition to its own IP address the SB5101 distributes exactly one address to whatever is connected to it - generally, a router. Those IP addresses do not originate from beyond the modem.


    Confusion understandably results when trying to diagnose problems like yours. If you bypass your Extreme by attaching a computer directly to the Surfboard so you can get online, then subsequently detach your computer and reattach the Extreme, it is certain not to work because the modem is not a router. It gave its one and only IP address to your computer and will continue to look for it at that address. Since it is no longer there, nothing happens. In the meantime your Extreme gets ignored, gives up, and assigns itself an IP address so nothing happens either. That's the reason for the power down.


    I have heard anecdotes that some modems that take a long time to reset themselves; thirty minutes or more, but that seems unreasonably long.

  • David Stahl Level 1 (0 points)

    I tried leaving everything unplugged for 8 hours and then for 13 hours after doing hard-resets. Still didn't work.


    I bought the cheapest Linksys/Cisco wireless router I could find and it worked perfectly out of the box with my cable modem. Any chance my Airport Extreme is busted and if so, how can I tell for sure?


    Would someone at an Apple Store be able to confirm that it's failed?

  • John Galt Level 8 (45,943 points)

    Yes, you did everything I can think of and the only conclusion I can draw is that the Extreme's WAN port is NG. This would appear consistent with everything else you did.


    It is strange that the failure would have coincided with the power going out.


    The Apple Store ought to be able to confirm your diagnosis.

  • F430 Level 1 (25 points)

    I ran into this very same issue just recently. My new Airport Express will only get a self-assigned IP address with the Surfboard modem. Funny enough, it works fine when I hooked it up to our U-Verse router so I know the unit is good.


    Even more strange is that our older Airport Express base station works just fine with the Surfboard. Multiple base station resets did not work at all.


    So now I'm using my old Airport Express and my new one is collecting dust until I can figure this out.

  • F430 Level 1 (25 points)

    Turns out my Airport Express was defective. Made an appointment with a Genius at the Apple Store and a fault immediately showed up on the diagnostic so Apple replaced it there on the spot. I was very happy.

  • Kippster2012 Level 1 (0 points)

    Your problem sounds a lot like mine.  Today I upgraded to faster internet and my 2 ipads, 2 laptops, and iMac were all working well prior to the exchange of cable modem to an Arris TM722 with a comcast reference on the side.  Now I can only connect the laptops individually the iPads are not connecting at all.  My wife just noticed that the phone was not working so I am hoping it is the cable modem my Airport is only a few months old.  Frustrating.

  • Bob Timmons Level 10 (98,184 points)

    Whenever you change the modem on a network, the AirPort router must be reset back to default settings and then set up again, so that it can associate with the new modem correctly.


    Did you do this?

  • Kippster2012 Level 1 (0 points)

    Thanks Bob I did eventually reset to factory and everything started working as it should.  I passed the info along to my internet service providers so they know what to do for the next Apple system user.