What is wrong with the wireless internet on this MacBook?

April 5, 2010 5:30 PM

If you can fix the incredibly frustrating wireless internet connection issues on my girlfriend's MacBook, we will both be your best friend!

(I've read other similar questions but none of them are quite the same as this).

For the past couple weeks, the wireless internet connection on my girlfriend's white MacBook has been really iffy. Mac OS X, version 10.5.8, 2 GHz Intel Core 2 Duo. Works well for two minutes, won't connect for two minutes, works well for six minutes, is sluggish for four minutes, etc. It's incredibly frustrating. Here are all pertinent details, some of which may not be related but just in case:

- The other computer in the house, a new 21.5 inch iMac, has not had any issues at all, same router and everything.
- The following message pops up occasionally on both computers simultaneously: "Ip Configuration: 192.168.1.6 in use by d4:9a:20:5c:88:99, DHCP Server 192.168.1.1" - I took a screenshot of one, but I believe they vary sometimes. I googled that error message, and as a result have tried renewing the DHCP lease (on both computers), but that didn't seem to help at all.
- This may not be related at all, but it did seem to start right after a MacBook SMC Firmware update 1.3 on March 8th. There was also an "AirPort Client update 2009-001, 1.0" at the same time.
- When she brought the computer to the place we were housesitting for a few weeks, there were no issues at all. My other computer was also at that house.
- I have restarted the router and modem several times. I also did a proper reset on the modem, and thought that had done the trick - but after maybe ten minutes of solid connection, it started all over again.
- My upstairs neighbor has access to our wireless signal. Could he have done something? Would changing the password do anything?
- The wireless signal itself never seems to waver (always 4 bars), and using the "diagnostics" in the system preferences it always claims the internet connection is working properly.

What the heck is going on? How can I fix this???? Don't hesitate to ask for any more details. HOPE ME!

posted by ORthey to computers & internet (22 answers total)

It's a problem with your router. What sort of router is it? Have you tried upgrading your router's firmware?
posted by signalnine at 5:41 PM on April 5, 2010

Some ideas:

When the network problems are happening, try checking the console (/Applications/Utilities/Console) for any error messages that look network-related.

Also check the Apple discussion forums (discussions.apple.com) for posts about that model of MacBook.

Try using it on a few more wireless networks (2 is a tiny sample size), see if you have the same problem.
posted by ripley_ at 5:43 PM on April 5, 2010

It is a Netgear router - and no, I have not thought of that. I'll investigate.
posted by ORthey at 5:43 PM on April 5, 2010

It's a problem with your router. What sort of router is it? Have you tried upgrading your router's firmware?

What? You really, really can't be sure about that. I've had similar problems on a similarly-aged MacBook Pro that eventually turned out to be a hardware defect on the wireless card itself.

Changing your router and upgrading the firmware is worth a try, but beware of anyone who says they know for sure what the problem is.
posted by ripley_ at 5:47 PM on April 5, 2010

One of the macs on my network has a problem that sounds like this. I suspect the router has trouble assigning IP addresses when computers go on and off the network, for example when a laptop leaves the house.

I've had limited success by going to network settings/advance settings and manually assigning an IP address rather than getting it from the DHCP server. This became a serious problem when I limited the number of IPs the router could give out at a time. Otherwise the solution has been to restart the router (just unplug it for a count of ten and plug it back in).
posted by smartyboots at 5:52 PM on April 5, 2010

Oh and I should have mentioned this before, but it has actually worked on 2 or 3 other networks without any issue - it's only here at my house that it hasn't been working right.

I've run network diagnostics a few times and each time in the console I get something like:

4/5/10 5:53:11 PM com.apple.launchd[67] (com.apple.NetworkDiagnostics[267]) Check-in of Mach service failed. Already active: com.apple.NetworkDiagnostic.agent
posted by ORthey at 5:55 PM on April 5, 2010

It sounds like you might have another device on your network trying to use the same IP as the MacBook, either because the router is crazy and telling multiple things to use one ip or because a device is set to a static IP within the dhcp range. This could be the iMac, a Wii, a television, an alarm clock, a toaster, seems like everything wants an IP nowadays. You could try setting the MacBook's IP to a different, static address as a test (go to system preferences, network, change from dhcp to static and use ip: 192.168.1.91, gateway 192.168.1.1, dns 192.168.1.1, subnet mask 255.255.255.0). If this works it's a conflict with another device on the network, but you'll still need to find and remedy the conflict and change the mb back to dhcp so it will work with other networks.
posted by contraption at 5:56 PM on April 5, 2010

Do you know who d4:9a:20:5c:88:99 is? If it's your upstairs neighbor's computer, it might be set up to use a fixed IP address that conflicts with something DHCP has handed out to one of yours.

DHCP servers usually try fairly hard to avoid this kind of address conflict - they will generally probe any IP address they're about to grant a lease for, and if they get a response, they'll pick a different IP address instead - but if the machine with the conflicting address happens not to be awake at the time the probe happens, conflicts can still occur.

Is your upstairs neighbor's access accidental or negotiated? If it's accidental, then you should certainly turn on WPA security and use a strong random password.

Checking your DHCP server's lease table will probably shed some light, too. Connect a web browser to 192.168.1.1 and poke around in your router's admin pages.

Another possibility: 192.168.1.x is a pretty common subnet address for routers. If your upstairs neighbor also has some kind of router, then it might well also be running its own DHCP server and handing out addresses that end up on the same subnet as yours and cause conflicts. So once you're in your own router's admin page, try changing its own address from 192.168.1.1 to something with a different subnet address by randomizing the third number e.g. 192.168.235.1. You will need to reset all your connections to it after doing this, so that all your computers and up leasing new IP addresses within the new subnet.
posted by flabdablet at 5:59 PM on April 5, 2010

We also have a netgear router and used to have a similar problem until I put on iPhone on a static ip address.
posted by advicepig at 6:03 PM on April 5, 2010

PS. I confirmed that the MAC address it was complaining about was my iPhone before I set it to use a static address.
posted by advicepig at 6:04 PM on April 5, 2010

Wow, thanks for all the answers. Looks like I have a lot to try - unfortunately some of these solutions are a bit over my head (not much of a computer guy) but I'll give it a shot.

To answer a couple questions/issues:

- We do have an iPod Touch in the house, but I think it's unlikely any other device (besides my computer) is using an IP address.
- The neighbor upstairs had my permission to use the network, I gave him the password.
posted by ORthey at 6:12 PM on April 5, 2010

Do you have a wireless phone? I had a similar problem when the apartment I was subletting had a 2.4Ghz (same band as wifi) phone next to the router.
posted by CharlesV42 at 6:14 PM on April 5, 2010

Change your router to use 192.168.2.x. If you still get messages about IP addresses in conflict, turn off DHCP and manually set your computers to 192.168.2.11 and 192.168.2.12. Finally, make sure you're not using the same channel as another router nearby -- this doesn't address your specific problem, but it is a good idea generally while you're in there changing the address range.
posted by davejay at 6:27 PM on April 5, 2010

Okay, it's /probably/ a router issue. It's impossible to tell for sure without some testing, but usually DHCP conflicts are in your router. I would suggest moving the DHCP start IP range up to 192.168.0.100. Most of the time static IPs for home networks are assigned below x.x.x.100. In this case, even if the NIC has a hardware issue that's forcing it to 192.168.0.7, the other DHCP clients will get assigned addresses out of that range and the problem will be resolved. Moving to a different subnet is not likely to fix your problem, you'll still get bad DHCP assignment from whatever was causing it before, now the device that's stuck on 192.168.1.7 will just not be able to talk to the rest of the network at all.
posted by signalnine at 6:57 PM on April 5, 2010

excuse me, I meant 192.168.1.6, in both of those.
posted by signalnine at 6:59 PM on April 5, 2010

unfortunately some of these solutions are a bit over my head

That's what we're here for. If you'd like to try something out but don't know what it means or how to go about it, post back for specific explanations and/or instructions.

Here's a little backgrounder (may contain traces of nuts) to get you started:

Every network interface has a MAC address (for Media Access Control, not Macintosh) burned in at the factory. MACs are six bytes long, and globally unique; by design, no two devices on the planet have the same MAC. The usual way to write out a MAC is as six groups of two hexadecimal digits e.g. d4:9a:20:5c:88:99.

The first three bytes of a MAC identify the manufacturer, and the last three are assigned by that manufacturer. d4:9a:20 is one of Apple's identifiers, for what it's worth.

MAC addresses allow devices that all share a common medium (such as a bunch of network cables on the same hub or switch, or the wireless virtual equivalent) to identify who is saying what to whom, but they're no use for routing network traffic beyond your LAN: there's nothing inherent in a MAC address that says that these addresses belong to devices on your own LAN while those addresses are only accessible via your modem. That's where IP addresses come in.

Every Internet-accessible device, and every device that uses Internet protocols for networking even when not connected to the Internet, needs an IP address to make that work. IP addresses are four bytes long, and conventionally written out as four groups of decimal digits e.g. 192.168.1.1 (each one of those numbers will be between 0 and 255, because those are all the unsigned numbers you can express with one byte).

An IP address has two parts: subnet address and host (e.g. computer) address. For 192.168.1.6, the subnet address is 192.168.1 and the host address is 6. Exactly which parts are considered subnet and which are considered host depends on too many things to explain here. For your purposes, the rules are: first two bytes must be 192.168; first three bytes are subnet; fourth byte is host.

If a device with an IP address (e.g. 192.168.1.3) wants to send a network packet to some other device (e.g. 192.168.1.6), it will check the other device's subnet address against its own. If they match, then it will assume that it can reach that other device directly on the LAN. If not, it knows that it needs to hand the packet off to its local gateway device (in your case, the modem/router at 192.168.1.1) instead of trying to do it directly.

To make this work, your LAN needs a way to match up IP addresses with MAC addresses, and make those matchings-up known to all players.

Making the matchings known is handled automatically by ARP, the Address Resolution Protocol: at any time, a device can broadcast an ARP request on the LAN that says something like "Who has 192.168.1.6? Tell 192.168.1.3." All LAN devices will receive that broadcast, and will be able to identify which MAC it came from. Then, whichever of them knows itself to be 192.168.1.6 will send an "I have 192.168.1.6" response back to 192.168.1.3 at the originating MAC address, and now both of those devices know how to translate both of those IP addresses into the corresponding MAC addresses and can communicate freely from that point on.

This beautiful scheme all falls in a heap if two different MACs have ended up matched with the same IP address. If you have two devices on your LAN, and you can tell they're different because they have different MAC addresses but they are both claiming to be 192.168.1.6, you can't really have a coherent IP conversation any more. The symptoms of this are pretty much what you describe. Your modem at 192.168.1.1, is having trouble conversing with 192.168.1.6 because 192.168.1.6 is actually two different computers.

Back in the Dark Ages, the initial matching-up of IP and MAC addresses was done by hand: each network device had to be manually assigned an IP address by the network administrator. This is called Static IP Addressing, and provided you have a competent netadmin and devices don't get moved from network to network it still works really well. But it's clearly no good for consumer-grade networking, where you want to plug stuff in and have it Just Work.

Which is where DHCP comes in. When a device joins a network and has no clue about what IP address it should use, it will broadcast a DHCP request on the LAN. If the LAN contains a DHCP server (and yours does - it's built into your router) then that server will see that broadcast, check the MAC address it came from against an internal table of MAC addresses it already knows about, and send a response telling the device with that MAC address which IP address to use and how long it's allowed to keep using it (this is what's called a DHCP Lease) what the local gateway address is, what IP address to use for domain name lookups and so forth.

This works really well unless (a) there are devices on the LAN with statically configured IP addresses, which are not visible to the DHCP server at the time it's handing out dynamic ones or (b) there is more than one DHCP server present, they can't see each other (perhaps due to wireless range issues) but they've both been configured to hand out IP addresses with the same subnet part.

Has that demystified the advice you're getting a little, or are you now even more confused than before?
posted by flabdablet at 7:29 PM on April 5, 2010 [9 favorites]

Before we get ahead of ourselves, let's do this in order:

1) Upgrade the Router's firmware. I'd give a 75% chance that this fixes your problem.
2) Change your WiFi password.
3) Modify the settings on your router's DHCP server so that it no longer distributes 192.168.1.6 as an address. You can do this by modifying the range of addresses it gives out (ie. start at 192.168.1.10 and count up from there), or switching to an entirely different subnet (ie. 192.168.2.xxx), although the latter will likely cause headaches.
4) Release/renew all of your computers. A reboot sometimes does the trick.
posted by schmod at 7:37 PM on April 5, 2010

flabdablet, that's an awesome explanation.
posted by azpenguin at 11:52 PM on April 5, 2010 [1 favorite]

We had the exact same thing using a couple of iphones, an old white MacBook and a new Macbook Pro on the same network. We noticed it would happen on some networks and not others and our symptoms were exactly as you described. We still notice the problem on the in-laws network... if I'm online, as soon as an older MacBook logs on, I have to reset my DHCP.

The reason I read on the 'net was that many routers have problems when different computers are accessing using different versions of the 802.11 standard.

We bought an airport extreme basestation and haven't had the problem again. It claims "Simultaneous dual-band Wi-Fi. " as one of its' features.
posted by dripdripdrop at 5:22 AM on April 6, 2010

I would try to rule out an easy and obvious answer - that your neighbour is hammering the connection. Uploading especially... if someone is uploading a file (eg bittorrent) it saturates the upstream bandwidth, and makes surfing for everyone else painfully slow.

Next time it happens, quickly change the wifi password and reboot the router. If that does fix it, you can have a word with him when he comes down to ask you why the internet isn't working! If not, just change the password back to what it was.
posted by derbs at 5:53 AM on April 6, 2010

Thank you all for the awesome answers. I haven't yet solved the problem (but I did want to highlight flabdablet's fantastic comment), but I will report back when I do. I'm sure one of these solutions will be the one!!
posted by ORthey at 3:44 PM on April 6, 2010

For the sake of anyone who might read through this in the future, even though this is super late, after trying all sorts of things in vain I finally just bought a new router - and our problems were solved. So all it took was $60! great!
posted by ORthey at 2:23 PM on October 12, 2010