MacBook – My Macbook Air won’t connect to the internet

Try using iStumbler to detect and identify neighboring and overlapping wireless access points (WAPs). It's likely an interference issue that can be solved with vigilance. You need to find out what channels your neighbor's WAPs are using, and then switch your router to use the least crowded channel you can find.

Ideally you want to use channels 1, 6, or 11. These are the channels that have the most leeway when it comes to other channels interfering with their signal. Wifi devices operating on a particular channel can interfere with other devices operating on channels up to 5 steps away. The amount of interference grows logarithmically with signal strength and channel proximity.

For example, if you are using channel 1 and your nearest neighboring wireless network is also using channel 1, you are receiving a large amount of interference. If you are on 1 and the other network is on 6, the interference is negligible. However, if you are on channel 1 and your neighbor is using channel 3, you are likely still on the receiving end of a huge amount of interference depending on their WAPs signal strength.

iStumbler will give you information about the signal strengths emanating from the other interfering WAPs, and from there you can infer the best channel to use. You may need to periodically perform the same task as your neighbors change their wifi channels.

The router IP might not be http://192.168.0.1

On your Mac go into System Preferences and select Network then Wi-Fi in the left hand list.

Just under the Status: line it should tell you your current IP address, make a note of it.

At the bottom right click on Advanced. Now select TCP/IP and Configure IPv4: should be set to Use DHCP. This pane will also tell you your router address a little further down.

Now you can point your browser to the correct IP address for your router and see what it is saying.

You can also open up Settings on your iPad and go to Wi-Fi then click on the little 'i' in a circle icon and it will tell you the IP address it is using and the address of the router.

If the IP address being used by both is the same then there's your problem.