Wi-fi issue

whodareswins

macrumors regular
Original poster
Jul 12, 2011
154
0
For a while now I have had an issue with wi-fi on my iMac. I thought it was router related but lately I have been testing it against my iPhone. What happens is that at seemingly random but frequent times (can happen 10 times a day) the internet connection drops. I still however stay connected, at full signal, to the wi-fi. It's just that I can't access any web pages at all or any web bases application. Internet usually comes back after a while but can sometimes stay dead for a while. All the while I can access the internet on my iPhone using the wi-fi. One thing I do to fix it straight away, is to turn airport off and on again and it works straight away.

Does anyone know what the issue could be? Do I need a new router?
 

r0k

macrumors 68040
Mar 3, 2008
3,612
73
Detroit
For a while now I have had an issue with wi-fi on my iMac. I thought it was router related but lately I have been testing it against my iPhone. What happens is that at seemingly random but frequent times (can happen 10 times a day) the internet connection drops. I still however stay connected, at full signal, to the wi-fi. It's just that I can't access any web pages at all or any web bases application. Internet usually comes back after a while but can sometimes stay dead for a while. All the while I can access the internet on my iPhone using the wi-fi. One thing I do to fix it straight away, is to turn airport off and on again and it works straight away.

Does anyone know what the issue could be? Do I need a new router?
Do you have Comcast? If so you might have the infamous Comcast DNS Flu. Go in your network settings in your router. Don't use the DNS servers provided by your ISP. Instead use google's 8.8.8.8 or opendns. Problem solved. You can also put these in your Mac and your iPhone but they really belong in your router so anything that uses your router gets google or opendns instead of Comcast or whatever is acting up. One way I spot this issue is to go in terminal and ping some known host like ping yahoo.com. Some hosts don't respond to ping but if the command fails to even start, then it can't even get the hostname, hence a dns issue.
 
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whodareswins

macrumors regular
Original poster
Jul 12, 2011
154
0
Do you have Comcast? If so you might have the infamous Comcast DNS Flu. Go in your network settings in your router. Don't use the DNS servers provided by your ISP. Instead use google's 8.8.8.8 or opendns. Problem solved. You can also put these in your Mac and your iPhone but they really belong in your router so anything that uses your router gets google or opendns instead of Comcast or whatever is acting up. One way I spot this issue is to go in terminal and ping some known host like ping yahoo.com. Some hosts don't respond to ping but if the command fails to even start, then it can't even get the hostname, hence a dns issue.
Thanks for your help, very much appreciated. I have not tested this so I will do once I finish work. Will this explain why it sometimes happens on our windows laptops?
 
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r0k

macrumors 68040
Mar 3, 2008
3,612
73
Detroit
Thanks for your help, very much appreciated. I have not tested this so I will do once I finish work. Will this explain why it sometimes happens on our windows laptops?
Yes. DNS flu affects all platforms and even internet ready TVs and game consoles.
 
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whodareswins

macrumors regular
Original poster
Jul 12, 2011
154
0
Yes. DNS flu affects all platforms and even internet ready TVs and game consoles.
I have assigned the router and my Mac googles DNS settings which seem to of made it better until yesterday. The internet connection died again. As before it stays connected to the router, just no internet connection. I pinged yahoo i think it was, an IP which i tested before (and worked) and it timed out. Any idea what the issue could be?
 
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r0k

macrumors 68040
Mar 3, 2008
3,612
73
Detroit
I have assigned the router and my Mac googles DNS settings which seem to of made it better until yesterday. The internet connection died again. As before it stays connected to the router, just no internet connection. I pinged yahoo i think it was, an IP which i tested before (and worked) and it timed out. Any idea what the issue could be?
When you can't ping an ip address, your internet is really down. You can check your router settings either in the web based interface (for non-Apple routers) or in Airport utility. You should be able to:

1 - Ping your router
2 - Ping your router's default gateway (on the internet - provided by your ISP)
3 - Ping a known ip address like 8.8.8.8 (google's dns servers)
4 - Ping a domain name like yahoo.com

If you have a Motorola cable modem, you can view its setup and remotely reset it at 192.168.100.1. Yes I know your internal ip range might be different, but the motorola modem will see this request and rather than route it to the internet, it will put up its setup page. This is a very good reason to never pick 192.168.100.0-255 for your own internal address range as it will confuse your router and it will not bother to pass the request along to your cable modem.
 
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