Why would Airport change subnet mask?

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Why would Airport change subnet mask?

Hello all.. kinda new to this stuff and was looking around for an answer, but couldn't find my exact situation. So, forgive me if I ask some stupid questions... Ok, I have MacBook Pro, and recently had to do a reset on my modem/router, and now this particular computer won't connect wirelessly. I also have a macbook air, and connects fine wirelessly. It seems I have narrowed it down to the subnet mask... maybe, but not completely sure. Just to be clear, I don't have the Airport express, I am just simply talking about the airport function built in to connect to a wireless network (not sure if it's called something different, or is the one on the actual computer just called airport?). So, going into the airport utility does nothing for me. It can't find any wireless devices. And everything I have read has been talking about going into that program and changing things. Anyways, I tried connecting automatically (using DHCP) and manually, but nothing helps. My macbook air gets a subnet mask of 255.255.255.0, while it has now started giving my macbook pro a 255.255.0.0. And I'm assuming my router is still configured for 255.255.255.0, but now my computer isn't.. How is that possible? Just wondering if anyone knew why this was happening and/or how I can fix it. Like I said, I'm not a genius with this stuff, but any help would be appreciated. Thanks for your help! And if I have missed any important information, let me know..

MacBook Pro, Mac OS X (10.6.7)

Posted on May 30, 2011 3:46 PM

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Answer 1

May 30, 2011 4:09 PM in response to jmjackson712

Unless you have an Apple-brand Wi-Fi base station, AirPort Utility is of no use to you.

It might help to reset the connection settings on your MacBook Pro using these steps one at a time until the problem is resolved, recognizing that, depending on your problem, not all of these steps will make sense:

1) Use the AirPort menu bar item to turn AirPort off, then on again.

2) Try to select your Wi-Fi network from the AirPort menu.

3) In the Network panel of System Preferences delete the AirPort item from the left column, then add it back.

4) In the same panel as (3), define a new location and see if you can make that work.

5) In the same panel, select the AirPort connection item, click the "Advanced" button, select the "TCP/IP" tab, then click "Renew DHCP Lease". Note that the fix this step implements may be temporary.

6) In the folder /Library/Preferences ( _not_ <yourhomefolder>/Library/Preferences), move the folder SystemConfiguration onto the Desktop, then restart your computer. See if you can now make your AirPort connection work.

These steps may not help, but they'll only take a couple of minutes to try. Before you try these, if you have any special network settings on your Mac for things like DSL credentials, note all your network settings, because the latter steps will destroy them. If you got all the way to the last step, if things don't work any worse than before, you can trash the saved SystemConfiguration folder.

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Answer 2

May 30, 2011 4:24 PM in response to jmjackson712

Hi,

On an Apple, the stuff to connect to a WiFi network is called Airport.

You set-up Airport on your Mac in : Apple - System Preferences - Network (as you already know)

The Airport Utility.app some people are referring to is only to set-up Apple Airport devices.

You are using a non-Apple router (no offense).

When DHCP is selected, forget about the subnet mask.

In System Preferences - Network have you already tried to delete the current settings (left pane) and create a new ?

Kind regards,

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Answer 3

May 30, 2011 4:32 PM in response to William-Boyd-Jr

Hi William,

Good info.

I didn't see your post... was still writing mine.

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Answer 4

jmjackson712 Author

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May 30, 2011 5:40 PM in response to William-Boyd-Jr

Thanks guys.. None of that worked. I had called at&t and went through all that with them, but still seen the mismatch of the subnet mask. When using DHCP, and it brings up the ip address and subnet mask, it brings up the wrong ip address (seems like it is a random one) and that different subnet mask. I just can't figure out if its my airport or if its something to do with my router? Seems like it would be my computer since my router is working wirelessly with my air. Thanks for the help though guys. Any other ideas?

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Answer 5

May 30, 2011 6:27 PM in response to jmjackson712

jmjackson712 wrote:

When using DHCP

On which device, your MacBook Pro or the (presumably) AT&T router?

it brings up the wrong ip address (seems like it is a random one)

Is that IP address in your LAN address range, or is it something like 169.254.x.x (a "self-assigned IP address")?

I just can't figure out if its my airport or if its something to do with my router?

Do you have any way to interrogate the configuration values of your router?

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Answer 6

jmjackson712 Author

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May 30, 2011 6:27 PM in response to jmjackson712

alright... so, I just connected to another network (my tethered droid), and my airport connected just fine to it, so, I'm thinking its the router not communicating correctly with my computer?

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Answer 7

jmjackson712 Author

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May 30, 2011 6:40 PM in response to William-Boyd-Jr

When using DHCP, on my Macbook, it gives me a random self assigned ip address (169.254.xxx.xxx). And yes, I can get into my router settings.. in fact, they're pretty complicated (ATT sent me a commercial type modem because their 2wire is a crappy modem.. lol.) Is there any particular setting on my router that would cause this? Thanks again.

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Answer 8

jmjackson712 Author

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May 30, 2011 6:51 PM in response to jmjackson712

alright!!!!! disregard, I figured it out. I think it was just some kind of hiccup with airport. I changed the name of my wireless network, and connected to it, and it hooked right up. Thanks guys for your help, I think my issue was probably a one of a kind thing. So, problem solved... Now on to figure out how to get my nat from 3 to 2 on my PS3.. Have a good night

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Answer 9

May 30, 2011 6:52 PM in response to jmjackson712

jmjackson712 wrote:

When using DHCP, on my Macbook, it gives me a random self assigned ip address (169.254.xxx.xxx).

That tells me that the router (not "modem", please) didn't respond to your Mac's DHCP request.

Is there any particular setting on my router that would cause this?

It's hard for me to imagine a setting that would cause your router to work well with one of your Macs but not the other. However, I'd check all the client DHCP settings, including those for subnet mask and starting and ending IP addresses.

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